The Experts below are selected from a list of 20010 Experts worldwide ranked by ideXlab platform
Richard J Maraia - One of the best experts on this subject based on the ideXlab platform.
-
La deletion from mouse brain alters pre trna metabolism and accumuLation of pre 5 8s rrna with neuron death and reactive astrocytosis
Molecular and Cellular Biology, 2017Co-Authors: Nathan H Blewett, James R Iben, Sergei Gaidamakov, Richard J MaraiaAbstract:: Human La Antigen (Sjogren's syndrome Antigen B [SSB]) is an abundant multifunctional RNA-binding protein. In the nucleopLasm, La binds to and protects from 3' exonucleases, the ends of precursor tRNAs, and other transcripts synthesized by RNA polymerase III and facilitates their maturation, while a nucleoLar isoform has been implicated in rRNA biogenesis by multiple independent lines of evidence. We showed previously that conditional La knockout (La cKO) from mouse cortex neurons results in defective tRNA processing, although the pathway(s) involved in neuronal loss thereafter was unknown. Here, we demonstrate that La is stably associated with a spliced pre-tRNA intermediate. Microscopic evidence of aberrant nuclear accumuLation of 5.8S rRNA in La cKO is supported by a 10-fold increase in a pre-5.8S rRNA intermediate. To identify pathways involved in subsequent neurodegeneration and loss of brain mass in the cKO cortex, we employed mRNA sequencing (mRNA-Seq), immunohistochemistry, and other approaches. This revealed robust enrichment of immune and astrocyte reactivity in La cKO cortex. Immunohistochemistry, including temporal analyses, demonstrated neurodegeneration, followed by astrocyte invasion associated with immune response and decreasing cKO cortex size over time. Thus, deletion of La from postmitotic neurons results in defective pre-tRNA and pre-rRNA processing and progressive neurodegeneration with loss of cortical brain mass.
-
nonphosphoryLated human La Antigen interacts with nucleolin at nucleoLar sites involved in rrna biogenesis
Molecular and Cellular Biology, 2004Co-Authors: Robert V Intine, Miroslav Dundr, Alex Vassilev, Elena Schwartz, Yingmin Zhao, Yingxin Zhao, Melvin L Depamphilis, Richard J MaraiaAbstract:La is a RNA-binding protein implicated in multiple pathways reLated to the production of tRNAs, ribosomal proteins, and other components of the transLational machinery (D. J. Kenan and J. D. Keene, Nat. Struct. Mol. Biol. 11:303-305, 2004). While most La is phosphoryLated and resides in the nucleopLasm, a fraction is in the nucleolus, the site of ribosome production, although the determinants of this localization are incompletely known. In addition to its conserved N-terminal domain, human La harbors a C-terminal domain that contains an atypical RNA recognition motif and a short basic motif (SBM) adjacent to phosphoserine-366. We report that nonphosphoryLated La (npLa) is concentrated in nucleoLar sites that correspond to the dense fibrilLar component that harbors nascent pol I transcripts as well as fibrilLarin and nucleolin, which function in early phases of rRNA maturation. Affinity purification and native immunoprecipitation of La and fluorescence resonance energy transfer in the nucleolus reveal close association with nucleolin. Moreover, La Lacking the SBM does not localize to nucleoli. Lastly, La exhibits SBM-dependent, phosphoryLation-sensitive interaction with nucleolin in a yeast two-hybrid assay. The data suggest that interaction with nucleolin is, at least in part, responsible for nucleoLar accumuLation of La and that npLa may be involved in ribosome biogenesis.
-
recognition of nascent rna by the human La Antigen conserved and divergent features of structure and function
Molecular and Cellular Biology, 2001Co-Authors: Richard J Maraia, Robert V IntineAbstract:La is a conserved RNA-binding phosphoprotein that interacts with a Large variety of ligands. The most ubiquitous function of La is association with newly synthesized RNA polymerase (Pol) III transcripts via their common UUU-OH 39 termini and stabilization of these against exonucleolytic digestion. AccumuLating evidence also indicates an activity for La in internal ribosome entry site-mediated transLation in mammalian cells and in the metabolism of a subset of 39-processed snRNA intermediates that end in uridyLates but are synthesized by Pol II. The most highly conserved region of La resides in the N-terminal domain (NTD), and this appears to mediate highaffinity UUU-OH recognition. As critically reviewed here by comparison to a consensus core RNA recognition motif (RRM) structure, the NTD can be modeled into a pair of tandem RRMs. In addition to the conserved NTD, human La (hLa) protein contains a C-terminal domain (CTD) that harbors a third RRM and a potential Walker A motif that appears to recognize the 59-ppp ends of nascent RNAs. The resulting bipartite mode of RNA binding can account for previously unexpLained observations and may underlie a unifying principle of La function. While a role for hLa in transcription remains controversial, its presence in a Pol III holoenzyme suggests a role reminiscent of the CTD of Pol II, as an integrator of transcriptional and posttranscriptional activities that include 59- and 39-RNA metabolism. Evidence that the 59-end-RNA recognition activity of hLa can be moduLated by phosphoryLation provides mechanistic insight into the signal transduction
-
Control of Transfer RNA Maturation by PhosphoryLation of the Human La Antigen on Serine 366
Molecular Cell, 2000Co-Authors: Robert V.a. Intine, Amy L Sakulich, John L Goodier, Shashi B. Koduru, Ying Huang, Erik Pierstorff, Lon Phan, Richard J MaraiaAbstract:Conversion of a nascent precursor tRNA to a mature functional species is a multipartite process that involves the sequential actions of several processing and modifying enzymes. La is the first protein to interact with pre-tRNAs in eukaryotes. An opal suppressor tRNA served as a functional probe to examine the activities of yeast and human (h)La proteins in this process in fission yeast. An RNA recognition motif and Walker motif in the metazoan-specific C-terminal domain (CTD) of hLa maintain pre-tRNA in an unprocessed state by blocking the 5'-processing site, impeding an early step in the pathway. Faithful phosphoryLation of hLa on serine 366 reverses this block and promotes tRNA maturation. The results suggest that reguLation of tRNA maturation at the level of RNase P cleavage may occur via phosphoryLation of serine 366 of hLa.
-
5 processing of trna precursors can be moduLated by the human La Antigen phosphoprotein
Molecular and Cellular Biology, 1998Co-Authors: Hao Fan, John L Goodier, Joel R Chamberlain, David R Engelke, Richard J MaraiaAbstract:Eukaryotic precursor (pre)-tRNAs are processed at both ends prior to maturation. Pre-tRNAs and other nascent transcripts synthesized by RNA polymerase III are bound at their 3′ ends at the sequence motif UUUOH [3′ oligo(U)] by the La Antigen, a conserved phosphoprotein whose role in RNA processing has been associated previously with 3′-end maturation only. We show that in addition to its role in tRNA 3′-end maturation, human La protein can also moduLate 5′ processing of pre-tRNAs. Both the La Antigen’s N-terminal RNA-binding domain and its C-terminal basic region are required for attenuation of pre-tRNA 5′ processing. RNA binding and nuclease protection assays with a variety of pre-tRNA substrates and mutant La proteins indicate that 5′ protection is a highly selective activity of La. This activity is dependent on 3′ oligo(U) in the pre-tRNA for interaction with the N-terminal RNA binding domain of La and interaction of the C-terminal basic region of La with the 5′ triphosphate end of nascent pre-tRNA. PhosphoryLation of La is known to occur on serine 366, adjacent to the C-terminal basic region. We show that this modification interferes with the La Antigen’s ability to protect pre-tRNAiMet from 5′ processing either by HeLa extract or purified RNase P but that it does not affect interaction with the 3′ end of pre-tRNA. These findings provide the first evidence to indicate that tRNA 5′-end maturation may be reguLated in eukaryotes. Implications of triphosphate recognition is discussed as is a role for La phosphoprotein in controlling transcriptional and posttranscriptional events in the biogenesis of polymerase III transcripts.
Tom P. Gordon - One of the best experts on this subject based on the ideXlab platform.
-
subcelluLar redistribution of La ssb autoAntigen during physiologic apoptosis in the fetal mouse heart and conduction system a clue to the pathogenesis of congenital heart block
Arthritis & Rheumatism, 2002Co-Authors: Hai B Tran, Maria Ohlsson, Dimitra Beroukas, Jenny Hiscock, J Bradley, Tom P. GordonAbstract:Objective In isoLated congenital heart block, the mechanism by which maternal autoantibodies target the intracelluLar components of the Ro/La RNP complex is unclear. Previous studies have demonstrated that cultured fetal cardiac myocytes rendered apoptotic bind antibodies to 48-kd La/SSB. This study further investigated the subcelluLar distribution of the La Antigen during apoptosis in the fetal mouse heart and conduction system. Methods The atrioventricuLar (AV) node, AV bundle, and sinoatrial (SA) node were identified in serial sections prepared from paraffin blocks of normal mouse fetuses on days 15, 17, and 19 of gestation. Apoptosis was detected by TUNEL assay. Under confocal microscopy, fluorescent Labeling of fragmented DNA in apoptotic cells was assessed by TUNEL, and La protein localization was visualized simultaneously using a murine monoclonal antibody or affinity-purified human polyclonal anti-La antibodies. Results Apoptotic cells were detected in and at the periphery of the AV and SA nodes as well as in the fetal heart valve insertions and working myocardium. In contrast, no apoptosis was detected in the adult heart AV node or surrounding myocardium. As expected, the La Antigen was predominantly immunolocalized to the nucleus in nonapoptotic cells. However, apoptotic cells showed a marked reduction of nuclear La and redistribution of La to the cytopLasm. High-resolution confocal microscopy revealed that in cells that had undergone apoptosis, La Antigen asymmetrically clustered near the surface of TUNEL-positive nuclei and apoptotic bodies. Conclusion These data provide the first in vivo demonstration of the subcelluLar translocation of La autoAntigen during apoptosis in the fetal heart and the conduction system under physiologic conditions. This observation supports the hypothesis that subcelluLar redistribution of La in the normally developing heart facilitates the binding of cognate maternal antibodies and subsequent tissue damage.
-
Hierarchical self-tolerance to T cell determinants within the ubiquitous nuclear self-Antigen La (SS-B) permits induction of systemic autoimmunity in normal mice.
The Journal of experimental medicine, 1996Co-Authors: Pakathip Reynolds, Tom P. Gordon, Anthony W. Purcell, David C. Jackson, James MccluskeyAbstract:Systemic autoimmune diseases are frequently associated with clustering of high titer autoantibody responses towards nuclear self-Antigens. Little is known, however, about the extent of immune tolerance to the target nuclear Antigens or the events leading to the complex autoantibody responses that are characteristic of systemic autoimmunity. To address these issues, we have examined the mouse immune response to La autoAntigen (mLa) and the homologous human La Antigen (hLa), which are components of the La(SS-B)/Ro(SS-A) ribonucleoprotein (RNP) complex targeted in systemic lupus erythematosus and primary Sjogren's syndrome. The findings reveal the presence of hierarchical T cell tolerance involving multiple autodeterminants within the La autoAntigen expressed by normal H-2k and H-2a mice. At one end of this spectrum, there was no detectable T or B cell autoimmunity observed in mice that were immunized with the immunodominant mLa287-301 determinant, which differed by a single residue in its core sequence from the homologous but highly immunogenic human La288-302 determinant. Interestingly, the mLa287-301 peptide acted as an altered peptide ligand that specifically antagonized the activation of an hLa288-302-specific T cell hybridoma. In contrast to the tolerogenic mLa287-301 determinant, a range of autoimmune potential was identified among poorly tolerizing, subdominant self-peptides present within mouse La autoAntigen. Notably, immunization of normal mice with the autologous subdominant La25-44 and La106-129 determinants resulted in limited or no detectable autoantibody response. In contrast, immunization with the subdominant mouse La13-30 determinant induced a proliferative T cell response associated with the appearance of specific autoantibodies recognizing multiple intrastructural (La) and intermolecuLar components (Ro) of the murine La/Ro RNP. The findings suggest how diversified autoimmunity might follow initiation of immunity to simple peptide mimics of poorly tolerogenic determinants that are present within ubiquitous self-Antigens.
-
intra and intermolecuLar spreading of autoimmunity involving the nuclear self Antigens La ss b and ro ss a
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Fiona Topfer, Tom P. Gordon, James MccluskeyAbstract:We have tested the extent of immune self-tolerance to the ubiquitously expressed nuclear/cytopLasmic autoAntigens La (SS-B) and Ro (SS-A) in healthy, nonautoimmune mice. Immunization of mice with recombinant mouse La resulted in a specific, isotype-switched autoantibody response, which was initially directed toward the La C subfragment (aa 111-242) but rapidly spread to involve the La A (aa 1-107) and La F (aa 243-345) regions of the La Antigen. IntramolecuLar spreading of the anti-La antibody response was further demonstrated by the appearance of autoantibodies to multiple, nonoverLapping Antigenic regions of La, after immunization of mice with the 107-aa La A subfragment. Moreover, immunization of mice with recombinant mouse or human La also elicited specific anti-60-kDa Ro IgG antibodies in all strains tested. Mice immunized with 60-kDa Ro produced a high titer anti-Ro antibody response, which was also associated with intermolecuLar spreading, resulting in the specific appearance of anti-La autoantibodies. These findings show that the development of autoantibodies to multiple components of the La/Ro ribonucleoprotein complex may follow initiation of immunity to a single component. In addition, the data reveal the incomplete nature of immune tolerance to La and Ro despite their endogenous expression in all nucleated cells. These observations are likely to account for the coexistence of anti-La/Ro antibodies in autoimmune disease and suggest a general expLanation for the appearance of mixed autoantibody patterns in systemic autoimmune disorders.
James Mccluskey - One of the best experts on this subject based on the ideXlab platform.
-
Hierarchical self-tolerance to T cell determinants within the ubiquitous nuclear self-Antigen La (SS-B) permits induction of systemic autoimmunity in normal mice.
The Journal of experimental medicine, 1996Co-Authors: Pakathip Reynolds, Tom P. Gordon, Anthony W. Purcell, David C. Jackson, James MccluskeyAbstract:Systemic autoimmune diseases are frequently associated with clustering of high titer autoantibody responses towards nuclear self-Antigens. Little is known, however, about the extent of immune tolerance to the target nuclear Antigens or the events leading to the complex autoantibody responses that are characteristic of systemic autoimmunity. To address these issues, we have examined the mouse immune response to La autoAntigen (mLa) and the homologous human La Antigen (hLa), which are components of the La(SS-B)/Ro(SS-A) ribonucleoprotein (RNP) complex targeted in systemic lupus erythematosus and primary Sjogren's syndrome. The findings reveal the presence of hierarchical T cell tolerance involving multiple autodeterminants within the La autoAntigen expressed by normal H-2k and H-2a mice. At one end of this spectrum, there was no detectable T or B cell autoimmunity observed in mice that were immunized with the immunodominant mLa287-301 determinant, which differed by a single residue in its core sequence from the homologous but highly immunogenic human La288-302 determinant. Interestingly, the mLa287-301 peptide acted as an altered peptide ligand that specifically antagonized the activation of an hLa288-302-specific T cell hybridoma. In contrast to the tolerogenic mLa287-301 determinant, a range of autoimmune potential was identified among poorly tolerizing, subdominant self-peptides present within mouse La autoAntigen. Notably, immunization of normal mice with the autologous subdominant La25-44 and La106-129 determinants resulted in limited or no detectable autoantibody response. In contrast, immunization with the subdominant mouse La13-30 determinant induced a proliferative T cell response associated with the appearance of specific autoantibodies recognizing multiple intrastructural (La) and intermolecuLar components (Ro) of the murine La/Ro RNP. The findings suggest how diversified autoimmunity might follow initiation of immunity to simple peptide mimics of poorly tolerogenic determinants that are present within ubiquitous self-Antigens.
-
intra and intermolecuLar spreading of autoimmunity involving the nuclear self Antigens La ss b and ro ss a
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Fiona Topfer, Tom P. Gordon, James MccluskeyAbstract:We have tested the extent of immune self-tolerance to the ubiquitously expressed nuclear/cytopLasmic autoAntigens La (SS-B) and Ro (SS-A) in healthy, nonautoimmune mice. Immunization of mice with recombinant mouse La resulted in a specific, isotype-switched autoantibody response, which was initially directed toward the La C subfragment (aa 111-242) but rapidly spread to involve the La A (aa 1-107) and La F (aa 243-345) regions of the La Antigen. IntramolecuLar spreading of the anti-La antibody response was further demonstrated by the appearance of autoantibodies to multiple, nonoverLapping Antigenic regions of La, after immunization of mice with the 107-aa La A subfragment. Moreover, immunization of mice with recombinant mouse or human La also elicited specific anti-60-kDa Ro IgG antibodies in all strains tested. Mice immunized with 60-kDa Ro produced a high titer anti-Ro antibody response, which was also associated with intermolecuLar spreading, resulting in the specific appearance of anti-La autoantibodies. These findings show that the development of autoantibodies to multiple components of the La/Ro ribonucleoprotein complex may follow initiation of immunity to a single component. In addition, the data reveal the incomplete nature of immune tolerance to La and Ro despite their endogenous expression in all nucleated cells. These observations are likely to account for the coexistence of anti-La/Ro antibodies in autoimmune disease and suggest a general expLanation for the appearance of mixed autoantibody patterns in systemic autoimmune disorders.
Hideaki Suda - One of the best experts on this subject based on the ideXlab platform.
-
defense responses of dentin pulp complex to experimentally induced caries in rat moLars an immunohistochemical study on kinetics of pulpal La Antigen expressing cells and macrophages
Journal of Endodontics, 1997Co-Authors: Abu Mohammed Mostafa Kamal, Takashi Okiji, Nobuyuki Kawashima, Hideaki SudaAbstract:Experimental caries was induced in rats that were innocuLated orally with Streptococcus mutants and maintained on a cariogenic diet. During the caries process, kinetics of the pulpal La Antigen-expressing cells and macrophages was monitored immunohistochemically and was correLated with caries depth and the status of reparative dentin formation. Initial pulpal response was characterized by a localized accumuLation of La Antigen-expressing cells beneath the dentinal tubules communicating with the superficial caries. This was followed by a caries-depth reLated increase of La Antigen-expressing cells and macrophages in the coronal pulp. The accumuLation of these cells under the dentin was most apparent when the caries had progressed into the reparative dentin. These findings suggest that the response of La Antigen-expressing cells to carious irritants triggers the defense reactions of the pulp. The intensity of the defense reactions may be correLated with the permeability of carious dentin.
-
Distribution of La Antigen-Expressing Nonlymphoid Cells in Various Stages of Induced Periapical Lesions in Rat MoLars
Journal of endodontics, 1994Co-Authors: Takashi Okiji, Nobuyuki Kawashima, T Kosaka, Chihiro Kobayashi, Hideaki SudaAbstract:Periapical lesions were experimentally produced in rat lower first moLars by exposing the pulp to the oral environment for 1 to 56 days. Temporal changes in the number and distribution of La Antigen-expressing nonlymphoid cells in the periapical tissue were examined immunohistochemically on decalcified cryostat sections using OX6, a monoclonal antibody against rat La Antigen. Influx of La-positive exudative cells into the periapical tissue was observed from 1 day postoperatively. Between 14 and 28 days when expansion of the periapical lesion was most evident, numerous La-positive macrophage-like and dendritic cell-like cells of diverse morphologies were found in the periapical tissue. The number of these cells showed further increase at 56 days postoperatively, when the lesion expansion had ceased. These results suggest the involvement of La Antigen-expressing nonlymphoid cells in the development and perpetuation of periapical pathosis. They may act primarily as Antigen-presenting cells, which are essential for the initiation of Antigen-specific immune defense.
-
an immunohistochemical study of the distribution of immunocompetent cells especially macrophages and ia Antigen expressing cells of heterogeneous popuLations in normal rat moLar pulp
Journal of Dental Research, 1992Co-Authors: Takashi Okiji, Nobuyuki Kawashima, T Kosaka, A Matsumoto, C Kobayashi, Hideaki SudaAbstract:The precise distribution of various immunocompetent cells in rat moLar pulp was immunohistochemically examined by use of seven anti-rat monoclonal antibodies. It was demonstrated that rat moLar pulp contained many 0X6 (anti-La Antigen-positive cells and a Large number of ED1 (anti-monocytes, macrophages, and dendritic cells)-positive, ED2 (anti-tissue macrophages)-positive, and/or OX35 (anti-macrophages and CD4+ lymphocytes)-positive cells, Macrophage-like cells predominated in the central portion of the pulp, while cells of dendritic appearance usually existed in the periphery of the pulp. Double-immunaperoxidase staining revealed that these cells showed some heterogeneity, but the majority could be cLassified as ED1+/0X6-/ED2+ cells, which may be Ia histiocytes. Findings also suggested that true dendritic cells may be included in the ED1+/0X6+/ED2- category of cells. A small number of T lymphocytes and pLasma cells were also detected. These results suggest that the normal dental pulp contains a variety ...
John L Goodier - One of the best experts on this subject based on the ideXlab platform.
-
Control of Transfer RNA Maturation by PhosphoryLation of the Human La Antigen on Serine 366
Molecular Cell, 2000Co-Authors: Robert V.a. Intine, Amy L Sakulich, John L Goodier, Shashi B. Koduru, Ying Huang, Erik Pierstorff, Lon Phan, Richard J MaraiaAbstract:Conversion of a nascent precursor tRNA to a mature functional species is a multipartite process that involves the sequential actions of several processing and modifying enzymes. La is the first protein to interact with pre-tRNAs in eukaryotes. An opal suppressor tRNA served as a functional probe to examine the activities of yeast and human (h)La proteins in this process in fission yeast. An RNA recognition motif and Walker motif in the metazoan-specific C-terminal domain (CTD) of hLa maintain pre-tRNA in an unprocessed state by blocking the 5'-processing site, impeding an early step in the pathway. Faithful phosphoryLation of hLa on serine 366 reverses this block and promotes tRNA maturation. The results suggest that reguLation of tRNA maturation at the level of RNase P cleavage may occur via phosphoryLation of serine 366 of hLa.
-
5 processing of trna precursors can be moduLated by the human La Antigen phosphoprotein
Molecular and Cellular Biology, 1998Co-Authors: Hao Fan, John L Goodier, Joel R Chamberlain, David R Engelke, Richard J MaraiaAbstract:Eukaryotic precursor (pre)-tRNAs are processed at both ends prior to maturation. Pre-tRNAs and other nascent transcripts synthesized by RNA polymerase III are bound at their 3′ ends at the sequence motif UUUOH [3′ oligo(U)] by the La Antigen, a conserved phosphoprotein whose role in RNA processing has been associated previously with 3′-end maturation only. We show that in addition to its role in tRNA 3′-end maturation, human La protein can also moduLate 5′ processing of pre-tRNAs. Both the La Antigen’s N-terminal RNA-binding domain and its C-terminal basic region are required for attenuation of pre-tRNA 5′ processing. RNA binding and nuclease protection assays with a variety of pre-tRNA substrates and mutant La proteins indicate that 5′ protection is a highly selective activity of La. This activity is dependent on 3′ oligo(U) in the pre-tRNA for interaction with the N-terminal RNA binding domain of La and interaction of the C-terminal basic region of La with the 5′ triphosphate end of nascent pre-tRNA. PhosphoryLation of La is known to occur on serine 366, adjacent to the C-terminal basic region. We show that this modification interferes with the La Antigen’s ability to protect pre-tRNAiMet from 5′ processing either by HeLa extract or purified RNase P but that it does not affect interaction with the 3′ end of pre-tRNA. These findings provide the first evidence to indicate that tRNA 5′-end maturation may be reguLated in eukaryotes. Implications of triphosphate recognition is discussed as is a role for La phosphoprotein in controlling transcriptional and posttranscriptional events in the biogenesis of polymerase III transcripts.
-
phosphoryLation of the human La Antigen on serine 366 can reguLate recycling of rna polymerase iii transcription complexes
Cell, 1997Co-Authors: Hao Fan, Amy L Sakulich, John L Goodier, Xiaolong Zhang, Jun Qin, Richard J MaraiaAbstract:The human La Antigen is an RNA-binding protein that facilitates transcriptional termination and reinitiation by RNA polymerase III. Native La protein fractionates into transcriptionally active and inactive forms that are unphosphoryLated and phosphoryLated at serine 366, respectively, as determined by enzymatic and mass spectrometric analyses. Serine 366 comprises a casein kinase II phosphoryLation site that resides within a conserved region in the La proteins from several species. RNA synthesis from isoLated transcription complexes is inhibited by casein kinase II-mediated phosphoryLation of La serine 366 and is reversible by dephosphoryLation. This work demonstrates a novel mechanism of transcriptional control at the level of recycling of stable transcription complexes.
