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T H Rabbitts - One of the best experts on this subject based on the ideXlab platform.
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LMO2 at 25 years a paradigm of chromosomal translocation proteins
Open Biology, 2015Co-Authors: J S Chambers, T H RabbittsAbstract:LMO2 was first discovered through proximity to frequently occurring chromosomal translocations in T cell acute lymphoblastic leukaemia (T-ALL). Subsequent studies on its role in tumours and in normal settings have highlighted LMO2 as an archetypical chromosomal translocation oncogene, activated by association with antigen receptor gene loci and a paradigm for translocation gene activation in T-ALL. The normal function of LMO2 in haematopoietic cell fate and angiogenesis suggests it is a master gene regulator exerting a dysfunctional control on differentiation following chromosomal translocations. Its importance in T cell neoplasia has been further emphasized by the recurrent findings of interstitial deletions of chromosome 11 near LMO2 and of LMO2 as a target of retroviral insertion gene activation during gene therapy trials for X chromosome-linked severe combined immuno-deficiency syndrome, both types of event leading to similar T cell leukaemia. The discovery of LMO2 in some B cell neoplasias and in some epithelial cancers suggests a more ubiquitous function as an oncogenic protein, and that the current development of novel inhibitors will be of great value in future cancer treatment. Further, the role of LMO2 in angiogenesis and in haematopoietic stem cells (HSCs) bodes well for targeting LMO2 in angiogenic disorders and in generating autologous induced HSCs for application in various clinical indications.
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requirement for lyl1 in a model of LMO2 driven early t cell precursor all
Blood, 2013Co-Authors: T H Rabbitts, Matthew P Mccormack, Jacob T Jackson, Benjamin James Shields, Chayanica Nasa, Nicholas J Slater, Cedric S Tremblay, David J CurtisAbstract:LMO2 is an oncogenic transcription factor that is frequently overexpressed in T-cell acute lymphoblastic leukemia (T-ALL), including early T-cell precursor ALL (ETP-ALL) cases with poor prognosis. LMO2 must be recruited to DNA by binding to the hematopoietic basic helix-loop-helix factors Scl/Tal1 or Lyl1. However, it is unknown which of these factors can mediate the leukemic activity of LMO2. To address this, we have generated LMO2-transgenic mice lacking either Scl or Lyl1 in the thymus. We show that although Scl is dispensable for LMO2-driven leukemia, Lyl1 is critical for all oncogenic functions of LMO2, including upregulation of a stem cell–like gene signature, aberrant self-renewal of thymocytes, and subsequent generation of T-cell leukemia. Lyl1 expression is restricted to preleukemic and leukemic stem cell populations in this model, providing a molecular explanation for the stage-specific expression of the LMO2-induced gene expression program. Moreover, LMO2 and LYL1 are coexpressed in ETP-ALL patient samples, and LYL1 is required for growth of ETP-ALL cell lines. Thus, the LMO2-LYL1 interaction is a promising therapeutic target for inhibiting self-renewing cancer stem cells in T-ALL, including poor-prognosis ETP-ALL cases.
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single domain intracellular antibodies from diverse libraries emphasizing dual functions of LMO2 protein interactions using a single vh domain
Journal of Biological Chemistry, 2011Co-Authors: Tomoyuki Tanaka, Helen Sewell, Simon Waters, Simon E V Phillips, T H RabbittsAbstract:Interfering intracellular antibodies are valuable for biological studies as drug surrogates and as potential macromolecular drugs per se. Their application is still limited because of the difficulty of acquisition of functional intracellular antibodies. We describe the use of the new intracellular antibody capture procedure (IAC3) to facilitate direct isolation of functional single domain antibody fragments using four independent target molecules (LMO2, TP53, CRAF1, and Hoxa9) from a set of diverse libraries. Initially, these have variability in only one of the three antigen-binding CDR regions of VH or VL and first round single domains are affinity matured by iterative randomization of the two other CDRs and reselection. We highlight the approach using a single domain binding to LMO2 protein. Our results show that interfering with LMO2 protein function demonstrates a role specifically in erythroid differentiation, confirm a necessary and sufficient function for LMO2 as a cancer therapy target in T-cell neoplasia and allowed for the first time production of soluble recombinant LMO2 protein by co-expression with intracellular domain antibodies. Co-crystallization of LMO2 and the anti-LMO2 VH protein was successful. These results demonstrate that this third generation IAC3 offers a robust toolbox for various biomedical applications and consolidates functional features of the LMO2 protein complex, which includes the importance of LMO2-Ldb1 protein interaction.
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the LMO2 oncogene initiates leukemia in mice by inducing thymocyte self renewal
Science, 2010Co-Authors: T H Rabbitts, Matthew P Mccormack, Lauren F Young, Sumitha Vasudevan, Carolyn A De Graaf, Rosalind Codrington, Stephen M Jane, David J CurtisAbstract:The LMO2 oncogene causes a subset of human T cell acute lymphoblastic leukemias (T-ALL), including four cases that arose as adverse events in gene therapy trials. To investigate the cellular origin of LMO2-induced leukemia, we used cell fate mapping to study mice in which the LMO2 gene was constitutively expressed in the thymus. LMO2 induced self-renewal of committed T cells in the mice more than 8 months before the development of overt T-ALL. These self-renewing cells retained the capacity for T cell differentiation but expressed several genes typical of hematopoietic stem cells (HSCs), suggesting that LMO2 might reactivate an HSC-specific transcriptional program. Forced expression of one such gene, Hhex, was sufficient to initiate self-renewal of thymocytes in vivo. Thus, LMO2 promotes the self-renewal of preleukemic thymocytes, providing a mechanism by which committed T cells can then accumulate additional genetic mutations required for leukemic transformation.
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targeting LMO2 with a peptide aptamer establishes a necessary function in overt t cell neoplasia
Cancer Research, 2009Co-Authors: Alex Appert, Lesley F Drynan, Tomoyuki Tanaka, Natividad Lobato, Eva Priego, Ricardo Nunez Miguel, T L Blundell, Helen Sewell, T H RabbittsAbstract:LMO2 is a transcription regulator involved in human T-cell leukemia, including some occurring in X-SCID gene therapy trials, and in B-cell lymphomas and prostate cancer. LMO2 functions in transcription complexes via protein-protein interactions involving two LIM domains and causes a preleukemic T-cell development blockade followed by clonal tumors. Therefore, LMO2 is necessary but not sufficient for overt neoplasias, which must undergo additional mutations before frank malignancy. An open question is the importance of LMO2 in tumor development as opposed to sustaining cancer. We have addressed this using a peptide aptamer that binds to the second LIM domain of the LMO2 protein and disrupts its function. This specificity is mediated by a conserved Cys-Cys motif, which is similar to the zinc-binding LIM domains. The peptide inhibits LMO2 function in a mouse T-cell tumor transplantation assay by preventing LMO2-dependent T-cell neoplasia. LMO2 is, therefore, required for sustained T-cell tumor growth, in addition to its preleukemic effect. Interference with LMO2 complexes is a strategy for controlling LMO2-mediated cancers, and the finger structure of LMO2 is an explicit focus for drug development. [Cancer Res 2009;69(11):4784–90]
Yasodha Natkunam - One of the best experts on this subject based on the ideXlab platform.
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LMO2 lim domain only 2 is expressed in a subset of acute myeloid leukaemia and correlates with normal karyotype
Histopathology, 2014Co-Authors: Jay L Patel, Yasodha Natkunam, Payam Pournazari, Sarahjoy Haggstrom, Farid Kosari, Meertaher Shabanirad, Adnan MansoorAbstract:Aim LMO2 is a transcription factor that plays a key role in haematopoiesis. Expression of LMO2 has been demonstrated in germinal centre B cells, various B cell lymphomas and T lymphoblastic lymphoma/leukaemia (T-ALL), but has not been studied extensively in acute myeloid leukaemia (AML). Methods We studied LMO2 expression by immunohistochemistry in biopsies from a cohort of AML patients (n = 196) and correlated it with established prognostic factors such as age, bone marrow morphology and cytogenetic findings. Results Forty per cent (79 of 196) of the samples from AML patients showed moderate/strong expression of LMO2 protein. LMO2 expression showed a significant positive correlation with normal cytogenetics (65% versus 24%, P < 0.0001) and a moderately negative correlation with complex karyotype [rs(98) = −0.218, P < 0.002]. AML associated with core binding factor [(t(8;21)/inv(16)/t(16;16)] had low LMO2 expression compared to diploid karyotype (29% versus 65%; P = 0.013). Expression of LMO2 protein exhibited an insignificant association with age (P = 0.197). Lower expression of LMO2 protein was noted in AML associated with myelodysplasia-related changes, compared to AML subtypes based on FAB classification (M0–M7) (21% versus 44%, P = 0.0187). Conclusions LMO2 is expressed in a subset of AML patients and is associated with normal karyotype, which is different from T-ALL, where specific translocation (11p13) mediates protein expression.
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identification of LMO2 transcriptome and interactome in diffuse large b cell lymphoma
Blood, 2012Co-Authors: Elena Cubedo, Xiaoyu Jiang, Andrew J Gentles, Chuanxin Huang, Yasodha Natkunam, Shruti Bhatt, Xiaoqing Lu, Isabel Romerocamarero, Aharon G Freud, Shuchun ZhaoAbstract:LMO2 regulates gene expression by facilitating the formation of multipartite DNA-binding complexes. In B cells, LMO2 is specifically up-regulated in the germinal center (GC) and is expressed in GC-derived non-Hodgkin lymphomas. LMO2 is one of the most powerful prognostic indicators in diffuse large B-cell (DLBCL) patients. However, its function in GC B cells and DLBCL is currently unknown. In this study, we characterized the LMO2 transcriptome and transcriptional complex in DLBCL cells. LMO2 regulates genes implicated in kinetochore function, chromosome assembly, and mitosis. Overexpression of LMO2 in DLBCL cell lines results in centrosome amplification. In DLBCL, the LMO2 complex contains some of the traditional partners, such as LDB1, E2A, HEB, Lyl1, ETO2, and SP1, but not TAL1 or GATA proteins. Furthermore, we identified novel LMO2 interacting partners: ELK1, nuclear factor of activated T-cells (NFATc1), and lymphoid enhancer-binding factor1 (LEF1) proteins. Reporter assays revealed that LMO2 increases transcriptional activity of NFATc1 and decreases transcriptional activity of LEF1 proteins. Overall, our studies identified a novel LMO2 transcriptome and interactome in DLBCL and provides a platform for future elucidation of LMO2 function in GC B cells and DLBCL pathogenesis.
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lim domain only 2 protein expression LMO2 germline genetic variation and overall survival in diffuse large b cell lymphoma in the pre rituximab era
Leukemia & Lymphoma, 2012Co-Authors: James R Cerhan, Yasodha Natkunam, Lindsay M Morton, Matthew J Maurer, Yan W Asmann, Thomas M Habermann, Mohammad A Vasef, Wendy Cozen, Charles F Lynch, Cristine AllmerAbstract:AbstractBoth LMO2 (LIM domain only 2) mRNA and protein expression in diffuse large B-cell lymphoma (DLBCL) have been associated with superior survival. However, a role for germline genetic variation in LMO2 has not been previously reported. Immunohistochemistry (IHC) for LMO2 was conducted on tumor tissue from diagnostic biopsies, and 20 tag single nucleotide polymorphisms (SNPs) from LMO2 were genotyped from germline DNA. LMO2 IHC positivity was associated with superior survival (hazard ratio [HR] = 0.55; 95% confidence interval [CI] 0.31–0.97). Four LMO2 SNPs (rs10836127, rs941940, rs750781, rs1885524) were associated with survival after adjusting for LMO2 IHC and clinical factors (p < 0.05), and one of these SNPs (rs941940) was also associated with IHC positivity (p = 0.02). Compared to a model with clinical factors only (c-statistic = 0.676), adding the four SNPs (c-statistic = 0.751) or LMO2 IHC (c-statistic = 0.691) increased the predictive ability of the model, while inclusion of all three factors ...
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identification of LMO2 transcriptome and interactome in diffuse large b cell lymphoma by integrated experimental and computational approach
Blood, 2011Co-Authors: Elena Cubedo, Xiaoyu Jiang, Andrew J Gentles, Chuanxin Huang, Yasodha Natkunam, Shruti Bhatt, Xiaoqing Lu, Isabel Romerocamarero, Sylvia K Plevritis, Jose A MartinezclimentAbstract:Abstract 438 The LMO2 is a cysteine-rich protein containing two zinc binding LIM domains indirectly regulating gene expression by mediating protein-protein interactions with other transcriptional factors (TFs), facilitating the formation of multipartite DNA-binding complexes. It is mainly expressed in endothelial and hematopoietic cells forming cell type specific complexes containing LDB1, TAL1, E2A and GATA2 proteins in endothelial cells and hematopoietic stem cells and LDB1, TAL-1, GATA1 and E proteins in the erythroid lineage. In these cells LMO2 is involved in angiogenesis and erythroid hematopoiesis. In T cells where LMO2 is only expressed in immature CD4/CD8 double-negative thymocytes, the LMO2 complex consist of LDB1, TAL1 and E2A, but may also bind to GATA3. Aberrant expression of LMO2 in T cells induces leukemogenesis. In the B cells, LMO2 is specifically up regulated in Germinal Center (GC) B cells. LMO2 is also expressed in GC-derived non-Hodgkin9s lymphomas and is one of the most powerful survival predictors in DLBCL patients. However, its function in GC B cells and DLBCL is currently unknown. In the present study we aimed to characterize the LMO2 transcriptome and interactome in DLBCL cells. Gene expression arrays were performed in Rck8 cells expressing low levels of endogenous LMO2, in which LMO2 was stably overexpressed to levels observed in GCB-like DLBCL. A total of 311 differentially expressed genes (DEGs) between control cell lines transfected with mock vector and LMO2 stably transfected samples were identified at FDR of 0.05. Sixty-four genes were down-regulated by LMO2 transfection, while 247 were up-regulated. Prominent amongst these were 27 genes encoding proteins of the histone cluster 1, colocalized on chromosome 6 and consistently higher expressed in LMO2 expressing cell lines. At the same time, multiple cell-cycle-related genes were also up-regulated by LMO2 transfection, including centromere proteins (CENPE, CENPI, and CENPN), the kinetochore associated protein NDC80 and the mitotic protein CDC25C. Expression of several randomly selected genes ( SPIC, LAX1, DLEU2, DOCK3, CHND2 and TNFRSF9 ) was validated by real time PCR and confirmed the observed gene expression changes upon LMO2 overexpression. To obtain a higher-level view of expression changes, we compared the list of DEGs to Gene Ontology (GO) categories. This revealed significant induction of genes involved in chromosome, nucleosome, and chromatin and protein-DNA complex assembly. We screened our microarray data against the Broad Institute Molecular Signatures Database, to identify TFs whose target genes were significantly up- or down-regulated by stable LMO2 transfection. This candidate list was filtered to include only those TFs whose target genes significantly overlapped with genes which had previously identified binding motifs for LMO2 complexes in their promoter sequences. Our analysis identified Sp1, NFAT, Elk1, and LEF1 as potential novel LMO2 co-factors, but not classical TAL1 and GATA partner proteins. We examined the expression of previously reported and new potential interaction partners of LMO2 in DLBCL cell lines and GC lymphocytes by Western blotting and analyzed the interaction of the expressed proteins with LMO2 by co-immunprecipitation. We identified that in DLBCL the LMO2 complex contains some of the traditional partners such as LDB1, E2A, HEB, lyl1 and ETO2, but not TAL1 or GATA proteins. Furthermore, we demonstrated LMO2 interaction also with SP1, ELK1, NFATc1 and LEF1 proteins. All the identified LMO2 interacting partners are also expressed in GC B lymphocytes, suggesting the presence of a similar protein complex in both normal and malignant B cells. LMO2 interaction with LEF protein affected its transcriptional activity, as measured by reporter assays. A Chromatin immunoprecipitation assay using promoter region of the DLEU2 gene, whose expression was up-regulated by LMO2 expression, confirmed the direct and specific LMO2 binding to a region harboring E2A and a SP1 binding sites. Overall, our studies identified an LMO2 transcriptome in DLBCL as well as its interactome, which contains novel previously unknown interacting partners. These findings suggest that LMO2 may affect unique and novel cellular functions in GC lymphocytes which may potentially contribute to DLBCL pathogenesis and are currently being investigated in our laboratory. Disclosures: No relevant conflicts of interest to declare.
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expression of LMO2 is associated with t 14 18 igh bcl2 fusion but not bcl6 translocations in diffuse large b cell lymphoma
American Journal of Clinical Pathology, 2010Co-Authors: David K Durnick, Izidore S Lossos, Yasodha Natkunam, Ronald Levy, Matthew J Maurer, Paul J Kurtin, Ellen D McphailAbstract:Diffuse large B-cell lymphoma (DLBCL) can be separated for prognostic purposes using gene expression profiling (GEP) into 2 subgroups: germinal center B-cell (GCB) and activated B-cell phenotypes. However, GEP is impractical for routine clinical use, and immunophenotyping is an imperfect surrogate. Therefore, we studied the relationship between expression of the purported germinal center marker LMO2 and the presence of IGH-BCL2 fusions, BCL6 translocations, and LMO2 translocations. In addition, we investigated the usefulness of LMO2 expression as a marker of GCB subtype in DLBCL. Immunohistochemical and fluorescence in situ hybridization studies were successfully performed on 101 cases of de novo DLBCL that had been incorporated into a tissue microarray. There was a statistically significant association between IGH-BCL2 fusion and LMO2 protein expression ( P = .02) but not between BCL6 translocations and LMO2 expression. LMO2 translocations were not identified. Although uncommon, all cases that had both IGH-BCL2 fusion and BCL6 translocations expressed LMO2. The findings suggest LMO2 as a potential marker for the GCB phenotype.
Matthew P Mccormack - One of the best experts on this subject based on the ideXlab platform.
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LMO2 induced murine t cell acute lymphoblastic leukemia frequently evolves to oncogene independence
Experimental Hematology, 2019Co-Authors: Matthew P Mccormack, Hesham Abdulla, Tenae Davies, Jacob T Jackson, Anh Vo, R Alserihi, Elizabeth M Viney, Tin Wong, Warren S Alexander, Ross A DickinsAbstract:LMO2 is an oncogenic transcription factor that is frequently overexpressed due to chromosomal abnormalities in T-cell acute lymphoblastic leukemia (T-ALL). In transgenic mouse models, LMO2 overexpression causes thymocyte self-renewal resulting in T-cell leukemia with long latency. However, the requirement for LMO2 for leukemia maintenance is poorly understood. To study this, we developed a Tetracycline-regulated knock-in mouse model that reversibly expresses LMO2 throughout the haematopoietic system. This led to a specific impairment of T-cell development and the development of self-renewing preleukemic stem cells (pre-LSCs) in the thymus. This was followed by the development of fully penetrant T-lymphoblastic leukemia resembling human T-ALL. In preleukemic mice, repression of LMO2 overcame the LMO2-induced thymocyte developmental block, reversed LMO2-induced gene expression changes and eliminated self-renewing pre-LSCs in vivo. Surprisingly however, the majority of LMO2-induced T-cell leukemias and leukemia-derived cell lines could be maintained in the absence of LMO2, implying an evolution of oncogene addiction that overcomes the requirement for LMO2. Leukemias that were LMO2-dependent expressed an immature gene expression profile similar to human Early T-cell Precursor-like ALL (ETP-ALL), but could not be predicted by assessment of immunophenotype or Notch pathway activation. The regulatable model used here will be useful to determine the molecular features associated with LMO2-dependence, along with critical components of LMO2-dependent and –independent self-renewal pathways in T-ALL.
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requirement for lyl1 in a model of LMO2 driven early t cell precursor all
Blood, 2013Co-Authors: T H Rabbitts, Matthew P Mccormack, Jacob T Jackson, Benjamin James Shields, Chayanica Nasa, Nicholas J Slater, Cedric S Tremblay, David J CurtisAbstract:LMO2 is an oncogenic transcription factor that is frequently overexpressed in T-cell acute lymphoblastic leukemia (T-ALL), including early T-cell precursor ALL (ETP-ALL) cases with poor prognosis. LMO2 must be recruited to DNA by binding to the hematopoietic basic helix-loop-helix factors Scl/Tal1 or Lyl1. However, it is unknown which of these factors can mediate the leukemic activity of LMO2. To address this, we have generated LMO2-transgenic mice lacking either Scl or Lyl1 in the thymus. We show that although Scl is dispensable for LMO2-driven leukemia, Lyl1 is critical for all oncogenic functions of LMO2, including upregulation of a stem cell–like gene signature, aberrant self-renewal of thymocytes, and subsequent generation of T-cell leukemia. Lyl1 expression is restricted to preleukemic and leukemic stem cell populations in this model, providing a molecular explanation for the stage-specific expression of the LMO2-induced gene expression program. Moreover, LMO2 and LYL1 are coexpressed in ETP-ALL patient samples, and LYL1 is required for growth of ETP-ALL cell lines. Thus, the LMO2-LYL1 interaction is a promising therapeutic target for inhibiting self-renewing cancer stem cells in T-ALL, including poor-prognosis ETP-ALL cases.
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the LMO2 oncogene initiates leukemia in mice by inducing thymocyte self renewal
Science, 2010Co-Authors: T H Rabbitts, Matthew P Mccormack, Lauren F Young, Sumitha Vasudevan, Carolyn A De Graaf, Rosalind Codrington, Stephen M Jane, David J CurtisAbstract:The LMO2 oncogene causes a subset of human T cell acute lymphoblastic leukemias (T-ALL), including four cases that arose as adverse events in gene therapy trials. To investigate the cellular origin of LMO2-induced leukemia, we used cell fate mapping to study mice in which the LMO2 gene was constitutively expressed in the thymus. LMO2 induced self-renewal of committed T cells in the mice more than 8 months before the development of overt T-ALL. These self-renewing cells retained the capacity for T cell differentiation but expressed several genes typical of hematopoietic stem cells (HSCs), suggesting that LMO2 might reactivate an HSC-specific transcriptional program. Forced expression of one such gene, Hhex, was sufficient to initiate self-renewal of thymocytes in vivo. Thus, LMO2 promotes the self-renewal of preleukemic thymocytes, providing a mechanism by which committed T cells can then accumulate additional genetic mutations required for leukemic transformation.
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the LMO2 t cell oncogene is activated via chromosomal translocations or retroviral insertion during gene therapy but has no mandatory role in normal t cell development
Molecular and Cellular Biology, 2003Co-Authors: Matthew P Mccormack, Lesley F Drynan, Richard Pannell, A Forster, T H RabbittsAbstract:The LMO2 gene encodes a LIM-only protein and is a target of chromosomal translocations in human T-cell leukemia. Recently, two X-SCID patients treated by gene therapy to rescue T-cell lymphopoiesis developed T-cell leukemias with retroviral insertion into the LMO2 gene causing clonal T-cell proliferation. In view of the specificity of LMO2 in T-cell tumorigenesis, we investigated a possible role for LMO2 in T-lymphopoiesis, using conditional knockout of mouse LMO2 with loxP-flanked LMO2 and Cre recombinase alleles driven by the promoters of the lymphoid-specific genes Rag1, CD19, and Lck. While efficient deletion of LMO2 was observed, even in the earliest detectable lymphoid cell progenitors of the bone marrow, there was no disturbance of lymphopoiesis in either T- or B-cell lineages, and in contrast to LMO2 transgenic mice, there were normal distributions of CD4− CD8− thymocytes. We conclude that there is no mandatory role for LMO2 in lymphoid development, implying that its specific role in T-cell tumorigenesis results from a reprogramming of gene expression after enforced expression in T-cell precursors.
Jacqueline M Matthews - One of the best experts on this subject based on the ideXlab platform.
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structural basis of simultaneous recruitment of the transcriptional regulators LMO2 and fog1 zfpm1 by the transcription factor gata1
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Lorna Wilkinsonwhite, Joel P Mackay, Roland Gamsjaeger, Siavoush Dastmalchi, Beeke Wienert, Philippa H Stokes, Merlin Crossley, Jacqueline M MatthewsAbstract:The control of red blood cell and megakaryocyte development by the regulatory protein GATA1 is a paradigm for transcriptional regulation of gene expression in cell lineage differentiation and maturation. Most GATA1-regulated events require GATA1 to bind FOG1, and essentially all GATA1-activated genes are cooccupied by a TAL1/E2A/LMO2/LDB1 complex; however, it is not known whether FOG1 and TAL1/E2A/LMO2/LDB1 are simultaneously recruited by GATA1. Our structural data reveal that the FOG1-binding domain of GATA1, the N finger, can also directly contact LMO2 and show that, despite the small size (< 50 residues) of the GATA1 N finger, both FOG1 and LMO2 can simultaneously bind this domain. LMO2 in turn can simultaneously contact both GATA1 and the DNA-binding protein TAL1/E2A at bipartite E-box/WGATAR sites. Taken together, our data provide the first structural snapshot of multiprotein complex formation at GATA1-dependent genes and support a model in which FOG1 and TAL1/E2A/LMO2/LDB1 can cooccupy E-box/WGATAR sites to facilitate GATA1-mediated activation of gene activation.
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assembly of the oncogenic dna binding complex LMO2 ldb1 tal1 e12
Proteins, 2007Co-Authors: Daniel P Ryan, Jaimee L Duncan, Philip W Kuchel, Jacqueline M MatthewsAbstract:The nuclear proteins TAL1 (T-cell acute leukaemia protein 1) and LMO2 (LIM-only protein 2) have critical roles in haematopoietic development, but are also often aberrantly activated in T-cell acute lymphoblastic leukaemia. TAL1 and LMO2 operate within multifactorial protein–DNA complexes that regulate gene expression in the developing blood cell. TAL1 is a tissue-specific basic helix–loop–helix (bHLH) protein that binds bHLH domains of ubiquitous E-proteins, (E12 and E47), to bind E-box (CANNTG) DNA motifs. TAL1bHLH also interacts specifically with the LIM domains of LMO2, which in turn bind Ldb1 (LIM-domain binding protein 1). Here we used biophysical methods to characterize the assembly of a five-component complex containing TAL1, LMO2, Ldb1, E12, and DNA. The bHLH domains of TAL1 and E12 alone primarily formed helical homodimers, but together preferentially formed heterodimers, to which LMO2 bound with high affinity (KA ∼ 108M−1). The resulting TAL1/E12/LMO2 complex formed in the presence or absence of DNA, but the different complexes preferentially bound different Ebox-sequences. Our data provide biophysical evidence for a mechanism, by which LMO2 and TAL1 both regulate transcription in normal blood cell development, and synergistically disrupt E2A function in T-cells to promote the onset of leukaemia. Proteins 2008. © 2007 Wiley-Liss, Inc.
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structural basis for the recognition of ldb1 by the n terminal lim domains of LMO2 and lmo4
The EMBO Journal, 2003Co-Authors: Janet E Deane, Joel P Mackay, Jane E Visvader, A K H Kwan, Jacqueline M MatthewsAbstract:LMO2 and LMO4 are members of a small family of nuclear transcriptional regulators that are important for both normal development and disease processes. LMO2 is essential for hemopoiesis and angiogenesis, and inappropriate overexpression of this protein leads to T-cell leukemias. LMO4 is developmentally regulated in the mammary gland and has been implicated in breast oncogenesis. Both proteins comprise two tandemly repeated LIM domains. LMO2 and LMO4 interact with the ubiquitous nuclear adaptor protein ldb1/NLI/CLIM2, which associates with the LIM domains of LMO and LIM homeodomain proteins via its LIM interaction domain (ldb1-LID). We report the solution structures of two LMO:ldb1 complexes (PDB: 1M3V and 1J2O) and show that ldb1-LID binds to the N-terminal LIM domain (LIM1) of LMO2 and LMO4 in an extended conformation, contributing a third strand to a β-hairpin in LIM1 domains. These findings constitute the first molecular definition of LIM-mediated protein–protein interactions and suggest a mechanism by which ldb1 can bind a variety of LIM domains that share low sequence homology.
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Structural basis for the recognition of ldb1 by the N‐terminal LIM domains of LMO2 and LMO4
The EMBO Journal, 2003Co-Authors: Janet E Deane, Joel P Mackay, Jane E Visvader, Ann H. Kwan, Jacqueline M MatthewsAbstract:LMO2 and LMO4 are members of a small family of nuclear transcriptional regulators that are important for both normal development and disease processes. LMO2 is essential for hemopoiesis and angiogenesis, and inappropriate overexpression of this protein leads to T-cell leukemias. LMO4 is developmentally regulated in the mammary gland and has been implicated in breast oncogenesis. Both proteins comprise two tandemly repeated LIM domains. LMO2 and LMO4 interact with the ubiquitous nuclear adaptor protein ldb1/NLI/CLIM2, which associates with the LIM domains of LMO and LIM homeodomain proteins via its LIM interaction domain (ldb1-LID). We report the solution structures of two LMO:ldb1 complexes (PDB: 1M3V and 1J2O) and show that ldb1-LID binds to the N-terminal LIM domain (LIM1) of LMO2 and LMO4 in an extended conformation, contributing a third strand to a β-hairpin in LIM1 domains. These findings constitute the first molecular definition of LIM-mediated protein–protein interactions and suggest a mechanism by which ldb1 can bind a variety of LIM domains that share low sequence homology.
Ronald Levy - One of the best experts on this subject based on the ideXlab platform.
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expression of LMO2 is associated with t 14 18 igh bcl2 fusion but not bcl6 translocations in diffuse large b cell lymphoma
American Journal of Clinical Pathology, 2010Co-Authors: David K Durnick, Izidore S Lossos, Yasodha Natkunam, Ronald Levy, Matthew J Maurer, Paul J Kurtin, Ellen D McphailAbstract:Diffuse large B-cell lymphoma (DLBCL) can be separated for prognostic purposes using gene expression profiling (GEP) into 2 subgroups: germinal center B-cell (GCB) and activated B-cell phenotypes. However, GEP is impractical for routine clinical use, and immunophenotyping is an imperfect surrogate. Therefore, we studied the relationship between expression of the purported germinal center marker LMO2 and the presence of IGH-BCL2 fusions, BCL6 translocations, and LMO2 translocations. In addition, we investigated the usefulness of LMO2 expression as a marker of GCB subtype in DLBCL. Immunohistochemical and fluorescence in situ hybridization studies were successfully performed on 101 cases of de novo DLBCL that had been incorporated into a tissue microarray. There was a statistically significant association between IGH-BCL2 fusion and LMO2 protein expression ( P = .02) but not between BCL6 translocations and LMO2 expression. LMO2 translocations were not identified. Although uncommon, all cases that had both IGH-BCL2 fusion and BCL6 translocations expressed LMO2. The findings suggest LMO2 as a potential marker for the GCB phenotype.
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the transcription factor LMO2 is a robust marker of vascular endothelium and vascular neoplasms and selected other entities
American Journal of Clinical Pathology, 2009Co-Authors: Dita Gratzinger, Izidore S Lossos, Shuchun Zhao, Robert B West, Robert V Rouse, Hannes Vogel, Ronald Levy, Yasodha NatkunamAbstract:The transcription factor LMO2 is involved in vascular and hematopoietic development and hematolymphoid neoplasia. We have demonstrated that LMO2 is expressed nearly ubiquitously in native and neoplastic vasculature, including lymphatics. LMO2 reactivity is otherwise virtually absent in nonhematolymphoid tissues except in breast myoepithelium, prostatic basal cells, and secretory phase endometrial glands. Vasculature is LMO2– in adult and fetal heart, brain of older adults, hepatic sinusoids, and hepatocellular carcinoma. LMO2 is uniformly expressed in benign vascular and lymphatic neoplasms and in most malignant vascular neoplasms with the exception of epithelioid vascular neoplasms of pleura and bone. Among nonvascular neoplasms, LMO2 reactivity is present in giant cell tumor of tendon sheath, juvenile xanthogranuloma, a subset of gastrointestinal stromal tumors, small round blue cell tumors, and myoepithelial-derived neoplasms. The restricted expression pattern, nuclear localization, and crisp staining of LMO2 in paraffin blocks make it an attractive candidate for the diagnostic immunohistochemistry laboratory. LMO2 is a member of a transcription factor family of proteins characterized by their cysteine-rich, zincbinding LIM domains. 1 Its expression is required early in hematopoiesis, 2 and its deregulation leads to T-cell leukemias resulting from chromosomal translocations and insertional mutations. 3,4 LMO2 expression is a strong predictor of superior outcome in patients with diffuse large B-cell lymphoma. 5,6 In addition to its pivotal roles in hematopoiesis and hematopoietic malignancy, LMO2 is required for angiogenesis early in development: the primitive vascular network formed by vasculogenesis does not undergo maturation into functional vascular structures in the absence of LMO2. 7 We recently developed a monoclonal anti-LMO2 antibody suitable for paraffin immunohistochemical studies 8 and demonstrated that the LMO2 protein is expressed in normal germinal center B cells and germinal center– derived B-cell lymphomas. We also observed expression of LMO2 in vascular endothelium, but not in other nonhematolymphoid tissues. 8
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LMO2 protein expression predicts survival in patients with diffuse large b cell lymphoma treated with immunochemotherapy rchop a multicenter validation study
Blood, 2008Co-Authors: Ranjana H Advani, Shuchun Zhao, Neha Talreja, Robert Tibshirani, Ash A Alizadeh, Javier Briones, R Bordes, J R Cohen, Sandra J Horning, Ronald LevyAbstract:Background: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous entity which necessitates the characterization of prognostic markers to better define risk groups. Previously, we showed that the expression of LMO2 mRNA was a strong predictor of superior outcome in patients with DLBCL in a multivariate model of six genes (Lossos et al, NEJM 2004). Subsequently, using a novel monoclonal anti-LMO2 antibody, we showed that LMO2 protein expression predicted outcome in DLBCL patients treated with anthracyline-based chemotherapy with and without rituximab (Natkunam et al, JCO 2008). For validation of our prior findings we analyzed an independent cohort of DLBCL patients treated with RCHOP that had not been included in our previous study. Methods : 106 patients with de novo DLBCL treated with RCHOP and followed for clinical outcome were included. Immunohistochemistry (IHC) for LMO2 was performed on tissue microarrays containing cores of biopsies obtained at initial diagnosis. Specimens expressing LMO2 in more than 30% of neoplastic cells were defined as positive. LMO2 expression was correlated with the international prognostic index (IPI), overall survival (OS) and progression free survival (PFS). Results : The median age of the study population was 58.5 years (24–85). The distribution of patients according to the IPI was 47% low risk (0–1 factors), 24% low intermediate (2 factors), 14% high intermediate (3 factors) and 15% high risk disease (>=4 factors). 70 patients (66%) were LMO2 positive (compared to 55% in our original study). 18 patients (17%) have died and the median survival has not been reached. At a median follow-up of 32 months the 2 year OS for LMO2 positive versus negative cases was 91% (95% confidence interval [CI] 0.84, 0.98) versus 70.8% (95% CI 0.558, 0.875) respectively, p=0.04. No significant difference was observed in the 2 year PFS between LMO2 positive versus negative cases. A multivariate Cox regression analysis that included IPI scores and LMO2 expression as dependent variables for OS demonstrated a trend for LMO2 (p=0.07) and significance for the IPI (p=0.046) as independent predictors for OS. For PFS only the IPI remained statistically significant (p=0.03). Conclusions : This study validates the prognostic impact of LMO2 protein expression in the RCHOP treatment era in an independent cohort of DLBCL patients. Despite the higher proportion of LMO2 positive cases in the current cohort, a relatively short follow-up and few adverse events, LMO2 protein expression was associated with improved OS. Continued clinical follow-up of this cohort is ongoing to fully assess the impact on outcome. Assessment of LMO2 protein expression by routine IHC in biopsy samples of newly diagnosed DLBCL may help identify patients with different outcomes. Clinical trials will be necessary to assess the optimal therapy for patients based on LMO2 status.
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the oncoprotein LMO2 is expressed in normal germinal center b cells and in human b cell lymphomas
Blood, 2007Co-Authors: Yasodha Natkunam, Izidore S Lossos, Shuchun Zhao, Behnaz Taidi, Jun Chen, David Y Mason, Margaret Jones, Anne Hammer, Stephen Hamilton Dutoit, Ronald LevyAbstract:We previously developed a multivariate model based on the RNA expression of 6 genes (LMO2, BCL6, FN1, CCND2, SCYA3, and BCL2) that predicts survival in diffuse large B-cell lymphoma (DLBCL) patients. Since LMO2 emerged as the strongest predictor of superior outcome, we generated a monoclonal anti-LMO2 antibody in order to study its tissue expression pattern. Immunohistologic analysis of over 1200 normal and neoplastic tissue and cell lines showed that LMO2 protein is expressed as a nuclear marker in normal germinal-center (GC) B cells and GC-derived B-cell lines and in a subset of GC-derived B-cell lymphomas. LMO2 was also expressed in erythroid and myeloid precursors and in megakaryocytes and also in lymphoblastic and acute myeloid leukemias. It was rarely expressed in mature T, natural killer (NK), and plasma cell neoplasms and was absent from nonhematolymphoid tissues except for endothelial cells. Hierarchical cluster analysis of immunohistologic data in DLBCL demonstrated that the expression profile of the LMO2 protein was similar to that of other GC-associated proteins (HGAL, BCL6, and CD10) but different from that of non-GC proteins (MUM1/IRF4 and BCL2). Our results warrant inclusion of LMO2 in multivariate analyses to construct a clinically applicable immunohistologic algorithm for predicting survival in patients with DLBCL.