The Experts below are selected from a list of 20121 Experts worldwide ranked by ideXlab platform
Mark Groudine - One of the best experts on this subject based on the ideXlab platform.
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activation of β major Globin Gene transcription is associated with recruitment of nf e2 to the β Globin lcr and Gene promoter
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Tomoyuki Sawado, Mark Groudine, Kazuhiko IgarashiAbstract:The mouse beta-Globin Gene locus control region (LCR), located upstream of the beta-Globin Gene cluster, is essential for the activated transcription of Genes in the cluster. The LCR contains multiple binding sites for transactivators, including Maf-recognition elements (MAREs). However, little is known about the specific proteins that bind to these sites or the time at which they bind during erythroid differentiation. We have performed chromatin immunoprecipitation experiments to determine the recruitment of the erythroid-specific transactivator p45 NF-E2/MafK (p18 NF-E2) heterodimer and small Maf proteins to various regions in the Globin Gene locus before and after the induction of murine erythroleukemia (MEL) cell differentiation. We report that, before induction, the LCR is occupied by small Maf proteins, and, on erythroid maturation, the NF-E2 complex is recruited to the LCR and the active Globin promoters, even though the promoters do not contain MAREs. This differentiation-coupled recruitment of NF-E2 complex correlates with a greater than 100-fold increase in beta-major Globin transcription, but is not associated with a significant change in locus-wide histone H3 acetylation. These findings suggest that the beta-Globin Gene locus exists in a constitutively open chromatin conformation before terminal differentiation, and we speculate that recruitment of NF-E2 complex to the LCR and active promoters may be a rate-limiting step in the activation of beta-Globin Gene expression.
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regulation of β Globin Gene expression straightening out the locus
Current Opinion in Genetics & Development, 1996Co-Authors: David I K Martin, Steven Fiering, Mark GroudineAbstract:Abstract A casual examination of the Globin literature would leave most readers with the impression that all aspects of β-Globin Gene regulation are controlled by the upstream locus control region (LCR). There is no clear evidence, however, that the LCR affects transcription in the β-Globin locus other than by altering its topology to maintain it in a state permissive for expression of the Globin Genes. Developmental switching of the Globin Genes may be independent of the LCR, relying only on elements close to the Genes and the arrangement of the Genes with respect to each other.
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Inactivation of the human beta-Globin Gene by targeted insertion into the beta-Globin locus control region.
Genes & development, 1992Co-Authors: Chul G. Kim, Elliot Epner, William C. Forrester, Mark GroudineAbstract:The human beta-Globin locus control region (LCR) is a complex regulatory element that controls the erythroid-specific expression of all cis-linked Globin Genes. The LCR is composed of five DNase I hypersensitive sites (HS) spanning 16 kb and located greater than 50 kb upstream of the beta-Globin Gene on chromosome 11. Constructs containing all or some of these HS have been shown to produce high-level erythroid-specific expression of linked Genes in transgenic mice and transfected cells. In all transgenic and transfection experiments reported to date, however, the spatial relationships between the LCR and Globin Genes have been disrupted. We have used homologous recombination (HR) as an approach to gain insights into the potential interactions between the LCR and Globin Genes in their native locations. A hygromycin B resistance (hygro(R)) Gene was inserted into the human beta-Globin LCR on chromosome 11 in a mouse/human hybrid erythroid cell line that expresses the human beta-Globin Gene after the induction of differentiation. As a consequence of this targeted insertion, the beta-Globin Gene is transcriptionally inactive and not inducible. In contrast, the hygro(R) Gene within the LCR is inducible, whereas randomly integrated hygro(R) Genes are not inducible in these cells. The chromatin structure of the targeted locus is also altered. A new DNase I HS is present in the enhancer/promoter of the hygro(R) Gene inserted into the LCR, whereas a HS normally present in the LCR 3' to the insertion is lost and the beta-Globin Gene promoter HS is not detectable. These results are consistent with the promoter/enhancer competition model for LCR function and Globin Gene switching.
Tim M Townes - One of the best experts on this subject based on the ideXlab platform.
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klf1 regulates bcl11a expression and gamma to beta Globin Gene switching
Nature Genetics, 2010Co-Authors: Dewang Zhou, Kaimao Liu, Chiaowang Sun, Kevin M Pawlik, Tim M TownesAbstract:We show that knockdown of KLF1 in human and mouse adult erythroid progenitors markedly reduces BCL11A levels and increases human γ-Globin/β-Globin expression ratios. These results suggest that KLF1 controls Globin Gene switching by directly activating β-Globin and indirectly repressing γ-Globin Gene expression. Controlled knockdown of KLF1 in adult erythroid progenitors may provide a method to activate fetal hemoGlobin expression in individuals with β-thalassemia or sickle cell disease.
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klf1 regulates bcl11a expression and gamma to beta Globin Gene switching
Nature Genetics, 2010Co-Authors: Dewang Zhou, Kaimao Liu, Chiaowang Sun, Kevin M Pawlik, Tim M TownesAbstract:We show that knockdown of KLF1 in human and mouse adult erythroid progenitors markedly reduces BCL11A levels and increases human gamma-Globin/beta-Globin expression ratios. These results suggest that KLF1 controls Globin Gene switching by directly activating beta-Globin and indirectly repressing gamma-Globin Gene expression. Controlled knockdown of KLF1 in adult erythroid progenitors may provide a method to activate fetal hemoGlobin expression in individuals with beta-thalassemia or sickle cell disease.
George Stamatoyannopoulos - One of the best experts on this subject based on the ideXlab platform.
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the 5 hs4 core element of the human beta Globin locus control region is required for high level Globin Gene expression in definitive but not in primitive erythropoiesis
Journal of Molecular Biology, 2001Co-Authors: Patrick A Navas, Kenneth R Peterson, Michael Mcarthur, George StamatoyannopoulosAbstract:To assess the contribution of DNase I-hypersensitive site 4 (HS4) of the beta-Globin locus control region (LCR) to overall LCR function we deleted a 280 bp fragment encompassing the core element of 5'HS4 from a 248 kb beta-Globin locus yeast artificial chromosome (beta-YAC) and analyzed Globin Gene expression during development in beta-YAC transgenic mice. Four transgenic lines were established; each contained at least one intact copy of the beta-Globin locus. The deletion of the 5'HS4 core element had no effect on Globin Gene expression during embryonic erythropoiesis. In contrast, deletion of the 5'HS4 core resulted in a significant decrease of gamma and beta-Globin Gene expression during definitive erythropoiesis in the fetal liver and a decrease of beta-Globin Gene expression in adult blood. We conclude that the core element of 5'HS4 is required for Globin Gene expression only in definitive erythropoiesis. Absence of the core element of HS4 may limit the ability of the LCR to provide an open chromatin domain and/or enhance gamma and beta-Globin Gene expression in the adult erythroid cells.
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developmental regulation of fetal to adult Globin Gene switching in human fetal erythroid mouse erythroleukemia cell hybrids
Developmental Biology, 1991Co-Authors: T Enver, M Brice, Joyce E Karlinsey, George Stamatoyannopoulos, Thalia PapayannopoulouAbstract:Abstract Human fetal erythroid × murine erythroleukemia cell hybrids undergo human fetal (γ) to adult (β) Globin Gene switching in vitro under the control of a mechanism located on human chromosome 11. We investigated whether this mechanism acts in cis or in trans by preparing hybrid cells containing marked fragments of the γ and β Genes known to switch in transgenic mice. In these cells the chromosomally introduced human Globin locus undergoes the fetal to adult Globin Gene switch. In contrast, the marked Globin Gene fragments were expressed at all stages of hybrid development. These results suggest that either the mechanism of switching acts in cis or that sequences present in the chromosomal Globin locus but missing from the transfected Globin Gene fragments mediate its action.
Stuart H Orkin - One of the best experts on this subject based on the ideXlab platform.
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Silencing of human fetal Globin expression is impaired in the absence of the adult beta-Globin Gene activator protein EKLF.
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Andrew C Perkins, Karin M.l. Gaensler, Stuart H OrkinAbstract:Abstract Globin Genes are subject to tissue-specific and developmental stage-specific regulation. A switch from human fetal (gamma)-to adult (beta)-Globin expression occurs within erythroid precursor cells of the adult lineage. Previously we and others showed by targeted Gene disruption that the zinc finger Gene, erythroid Kruppel-like factor (EKLF), is required for expression of the beta-Globin Gene in mice, presumably through interaction with a high-affinity binding site in the proximal promoter. To examine the role of EKLF in the developmental regulation of the human gamma-Globin Gene we interbred EKLF heterozygotes (+/-) with mice harboring a human beta-Globin yeast artificial chromosome transGene. We find that in the absence of EKLF, while human beta-Globin expression is dramatically reduced, gamma-Globin transcripts are elevated approximately 5-fold. Impaired silencing of gamma-Globin expression identifies EKLF as the first transcription factor participating quantitatively in the gamma-Globin to beta-Globin switch. Our findings are compatible with a competitive model of switching in which EKLF mediates an adult stage-specific interaction between the beta-Globin Gene promoter and the locus control region that excludes the gamma-Globin Gene.
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dependence of Globin Gene expression in mouse erythroleukemia cells on the nf e2 heterodimer
Molecular and Cellular Biology, 1995Co-Authors: K J Kotkow, Stuart H OrkinAbstract:High-level, tissue-specific expression of the beta-Globin Genes requires the presence of an upstream locus control region (LCR). The overall enhancer activity of the beta-Globin complex LCR (beta-LCR) is dependent on the integrity of the tandem NF-E2 sites of HS-2. The NF-E2 protein which binds these sites is a heterodimeric basic leucine zipper protein composed of a tissue-specific subunit, p45 NF-E2, and a smaller subunit, p18 NF-E2, that is widely expressed. In these studies, we sought to investigate the role of NF-E2 in Globin expression. We show that expression of a dominant-negative mutant p18 greatly reduces the amount of functional NF-E2 complex in the cell. Reduced levels of both alpha- and beta-Globin were associated with the lower levels of NF-E2 activity in this cell line. Globin expression was fully restored upon the introduction of a tethered p45-p18 heterodimer. We also examined CB3 cells, a mouse erythroleukemia (MEL) cell line that does not express endogenous p45 NF-E2, and demonstrated that the restoration of Globin Gene expression was dependent upon the levels of expressed tethered NF-E2 heterodimer. Results of DNase I hypersensitivity mapping and in vivo footprinting assays showed no detectable chromatin alterations in beta-LCR HS-2 due to loss of NF-E2. Finally, we examined the specificity of NF-E2 for Globin Gene expression in MEL cells. These experiments indicate a critical role for the amino-terminal domain of p45 NF-E2 and show that a related protein, LCRF1, is unable to restore Globin Gene expression in p45 NF-E2-deficient cells. From these results, we conclude that NF-E2 is specifically required for high level goblin Gene expression in MEL cells.
Aurelio Maggio - One of the best experts on this subject based on the ideXlab platform.
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analysis of delta Globin Gene alleles in the sicilian population identification of five new mutations
Haematologica, 2006Co-Authors: Antonino Giambona, Cristina Passarello, Gaetano Ruggeri, Disma Renda, Pietro Teresi, Maurizio Anza, Aurelio MaggioAbstract:Although delta-Globin Gene (HBD MIM#142000) mutations have no clinical implications, co-inheritance of beta- and delta-thalassemia may lead to misdiagnosis. Among 7,153 samples studied for beta-thalassemia, 205 samples with lower than expected HbA2 levels were selected for our analysis and 183 samples (2.5%) were positive for delta-Globin Gene mutations. Twelve different mutations were detected, and among these five have not been not previously described (HbA2-Catania HBD c.8A-->T, HbA2-Corleone HBD c.41C-->A, HbA2-Ventimiglia HBD c.212C-->G, HbA2-Montechiaro HBD c.260C-->A, and HbA2-Bagheria HBD c.422C-->T). This study suggests that delta-Globin Gene defects are very common in Sicily. Thus, these mutations need to be considered during beta-thalassemia screening to avoid false negative results in the detection of at-risk couples.
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Evidence for a Globin promoter-specific silencer element located upstream of the human delta-Globin Gene.
Biochemical and biophysical research communications, 1994Co-Authors: Maria Vitale, R. Di Marzo, Roberta Calzolari, S. Acuto, D O'neill, Arthur Bank, Aurelio MaggioAbstract:We describe the negative regulatory activity of a 1.7 kilobase (kb) region (R) in the human beta-Globin locus located between 4.0 and 2.3 kb upstream of the delta-Globin Gene capsite, using a transient assay with the chloramphenicol acetyltransferase (CAT) reporter Gene in mouse erythroleukemia (MEL) cells. The R region is deleted in most cases of deletion hereditary persistence of fetal hemoGlobin (HPFH), but is unaffected in most delta beta zero-thalassemias. However, no experiments addressing its function in Globin Gene expression have been reported to date. We show that R inhibits CAT expression of constructs containing a fetal (gamma) or adult (beta) Globin Gene promoter, but does not affect expression of similar constructs using a non-Globin (SV40) promoter. The inhibitory effect on the beta-Globin promoter can be localized to a 651 bp sub-region of R. For the gamma-Globin promoter, no sub-region of R can reproduce the level of inhibition associated with the entire region.