The Experts below are selected from a list of 13833 Experts worldwide ranked by ideXlab platform
Melanie Ehrlich - One of the best experts on this subject based on the ideXlab platform.
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Histone modification in constitutive heterochromatin versus unexpressed Euchromatin in human cells.
Journal of cellular biochemistry, 2004Co-Authors: Guanchao Jiang, Fan Yang, Cecilia G. Sanchez, Melanie EhrlichAbstract:Histone modifications are implicated in regulating chromatin condensation but it is unclear how they differ between constitutive heterochromatin and unexpressed Euchromatin. Chromatin immunoprecipitation (ChIP) assays were done on various human cell populations using antibodies specific for acetylated or methylated forms of histone H3 or H4. Analysis of the immunoprecipitates was by quantitative real-time PCR or semi-quantitative PCR (SQ- PCR). Of eight tested antibodies, the one for histone H4 acetylated at lysine 4, 8, 12, or 16 was best for distinguishing constitutive heterochromatin from unexpressed Euchromatin, but differences in the extent of immunoprecipitation of thesetwotypesofchromatinwereonlymodest,althoughhighlyreproducible.Withthisantibody,therewasanaverageof 2.5-fold less immunoprecipitation of three constitutive heterochromatin regions than of four unexpressed euchromatic gene regions and about 15-fold less immunoprecipitation of these heterochromatin standards than of two constitutively expressed gene standards (P
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histone modification in constitutive heterochromatin versus unexpressed Euchromatin in human cells
Journal of Cellular Biochemistry, 2004Co-Authors: Guanchao Jiang, Fan Yang, Cecilia Sanchez, Melanie EhrlichAbstract:Histone modifications are implicated in regulating chromatin condensation but it is unclear how they differ between constitutive heterochromatin and unexpressed Euchromatin. Chromatin immunoprecipitation (ChIP) assays were done on various human cell populations using antibodies specific for acetylated or methylated forms of histone H3 or H4. Analysis of the immunoprecipitates was by quantitative real-time PCR or semi-quantitative PCR (SQ- PCR). Of eight tested antibodies, the one for histone H4 acetylated at lysine 4, 8, 12, or 16 was best for distinguishing constitutive heterochromatin from unexpressed Euchromatin, but differences in the extent of immunoprecipitation of thesetwotypesofchromatinwereonlymodest,althoughhighlyreproducible.Withthisantibody,therewasanaverageof 2.5-fold less immunoprecipitation of three constitutive heterochromatin regions than of four unexpressed euchromatic gene regions and about 15-fold less immunoprecipitation of these heterochromatin standards than of two constitutively expressed gene standards (P <0.001). We also analyzed histone acetylation and methylation by immunocytochemistry with antibodies to H4 acetylated at lysine 8, H3 trimethylated at lysine 9, and H3 methylated at lysine 4. In addition, immunocytochemical analysis was done with an antibody to heterochromatin protein 1a (HP1a), whose preferential binding to heterochromatin has been linked to trimethylation of H3 at lysine 9. Our combined ChIP and immuno- cytochemicalresultssuggestthatfactorsotherthanhypoacetylationoftheN-terminaltailsofH4andhypermethylationof H3 at lysine 9 can play an important role in determining whether a chromatin sequence in mammalian cells is constitutively heterochromatic. J. Cell. Biochem. 93: 286-300, 2004. 2004 Wiley-Liss, Inc.
Sue Iggins - One of the best experts on this subject based on the ideXlab platform.
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an e3 ubiquitin ligase prevents ectopic localization of the centromeric histone h3 variant via the centromere targeting domain
Molecular Cell, 2010Co-Authors: Prerana Ranjitka, Maximilia O Press, Richard E Ake, Michael J Maccoss, Sue IgginsAbstract:Summary Proper centromere function is critical to maintain genomic stability and to prevent aneuploidy, a hallmark of tumors and birth defects. A conserved feature of all eukaryotic centromeres is an essential histone H3 variant called CENP-A that requires a centromere targeting domain (CATD) for its localization. Although proteolysis prevents CENP-A from mislocalizing to Euchromatin, regulatory factors have not been identified. Here, we identify an E3 ubiquitin ligase called Psh1 that leads to the degradation of Cse4, the budding yeast CENP-A homolog. Cse4 overexpression is toxic to psh1 Δ cells and results in euchromatic localization. Strikingly, the Cse4 CATD is a key regulator of its stability and helps Psh1 discriminate Cse4 from histone H3. Taken together, we propose that the CATD has a previously unknown role in maintaining the exclusive localization of Cse4 by preventing its mislocalization to Euchromatin via Psh1-mediated degradation.
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proteolysis contributes to the exclusive centromere localization of the yeast cse4 cenp a histone h3 variant
Current Biology, 2004Co-Authors: Kimberly A. Collins, Suzanne Furuyama, Sue IgginsAbstract:Abstract Kinetochores are the specialized protein structures that form on centromeric DNA and direct chromosome segregation. It is critical that all chromosomes assemble a single kinetochore every cell cycle. One hallmark of all eukaryotic kinetochores is CENP-A, an essential centromeric histone H3 (CenH3) variant. Overexpression of CENP-A causes mislocalization to Euchromatin, which could lead to deleterious consequences because CENP-A overexpression is associated with colorectal cancer [1, 2]. Although CENP-A protein levels are important for genomic stability, little is known about the mechanisms of CenH3 regulation. Here, we show that the levels of the budding yeast CenH3, Cse4, are regulated by ubiquitin-proteasome-mediated proteolysis. Because mutation of all Cse4 lysine residues did not completely stabilize the protein, we isolated a dominant lethal mutant, CSE4-351 , that was stable. The Cse4-351 protein localized to Euchromatin, suggesting that proteolysis prevents CenH3 euchromatic localization. When wild-type Cse4 was fused to a degron signal, the soluble Cse4 protein was rapidly degraded, but the centromere bound Cse4 was stable, indicating that centromere localization protects Cse4 from degradation. Taken together, these data identify proteolysis as one mechanism that contributes to the restricted centromere localization of the yeast CenH3.
Hiten D. Madhani - One of the best experts on this subject based on the ideXlab platform.
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a protein complex containing the conserved swi2 snf2 related atpase swr1p deposits histone variant h2a z into Euchromatin
PLOS Biology, 2004Co-Authors: Michael S Kobor, Marc D. Meneghini, Hiten D. Madhani, Shivkumar Venkatasubrahmanyam, Jennifer L Jennings, Andrew J Link, Jennifer W Gin, Jasper RineAbstract:The conserved histone variant H2A.Z functions in Euchromatin to antagonize the spread of heterochromatin. The mechanism by which histone H2A is replaced by H2A.Z in the nucleosome is unknown. We identified a complex containing 13 different polypeptides associated with a soluble pool of H2A.Z in Saccharomyces cerevisiae. This complex was designated SWR1-Com in reference to the Swr1p subunit, a Swi2/Snf2-paralog. Swr1p and six other subunits were found only in SWR1-Com, whereas six other subunits were also found in the NuA4 histone acetyltransferase and/or the Ino80 chromatin remodeling complex. H2A.Z and SWR1 were essential for viability of cells lacking the EAF1 component of NuA4, pointing to a close functional connection between these two complexes. Strikingly, chromatin immunoprecipitation analysis of cells lacking Swr1p, the presumed ATPase of the complex, revealed a profound defect in the deposition of H2A.Z at euchromatic regions that flank the silent mating type cassette HMR and at 12 other chromosomal sites tested. Consistent with a specialized role for Swr1p in H2A.Z deposition, the majority of the genome-wide transcriptional defects seen in swr1Delta cells were also found in htz1Delta cells. These studies revealed a novel role for a member of the ATP-dependent chromatin remodeling enzyme family in determining the region-specific histone subunit composition of chromatin in vivo and controlling the epigenetic state of chromatin. Metazoan orthologs of Swr1p (Drosophila Domino; human SRCAP and p400) may have analogous functions.
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a protein complex containing the conserved swi2 snf2 related atpase swr1p deposits histone variant h2a z into Euchromatin
PLOS Biology, 2004Co-Authors: Michael S Kobor, Marc D. Meneghini, Hiten D. Madhani, Shivkumar Venkatasubrahmanyam, Jennifer L Jennings, Andrew J Link, Jasper RineAbstract:The conserved histone variant H2A.Z functions in Euchromatin to antagonize the spread of heterochromatin. The mechanism by which histone H2A is replaced by H2A.Z in the nucleosome is unknown. We identified a complex containing 13 different polypeptides associated with a soluble pool of H2A.Z in Saccharomyces cerevisiae. This complex was designated SWR1-Com in reference to the Swr1p subunit, a Swi2/Snf2-paralog. Swr1p and six other subunits were found only in SWR1-Com, whereas six other subunits were also found in the NuA4 histone acetyltransferase and/or the Ino80 chromatin remodeling complex. H2A.Z and SWR1 were essential for viability of cells lacking the EAF1 component of NuA4, pointing to a close functional connection between these two complexes. Strikingly, chromatin immunoprecipitation analysis of cells lacking Swr1p, the presumed ATPase of the complex, revealed a profound defect in the deposition of H2A.Z at euchromatic regions that flank the silent mating type cassette HMR and at 12 other chromosomal sites tested. Consistent with a specialized role for Swr1p in H2A.Z deposition, the majority of the genome-wide transcriptional defects seen in swr1Δ cells were also found in htz1Δ cells. These studies revealed a novel role for a member of the ATP-dependent chromatin remodeling enzyme family in determining the region-specific histone subunit composition of chromatin in vivo and controlling the epigenetic state of chromatin. Metazoan orthologs of Swr1p (Drosophila Domino; human SRCAP and p400) may have analogous functions.
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Conserved Histone Variant H2A.Z Protects Euchromatin from the Ectopic Spread of Silent Heterochromatin
Cell, 2003Co-Authors: Marc D. Meneghini, Hiten D. MadhaniAbstract:Boundary elements hinder the spread of heterochromatin, yet these sites do not fully account for the preservation of adjacent Euchromatin. Histone variant H2A.Z (Htz1 in yeast) replaces conventional H2A in many nucleosomes. Microarray analysis revealed that HTZ1-activated genes cluster near telomeres. The reduced expression of most of these genes in htz1Δ cells was reversed by the deletion of SIR2 (sir2Δ) suggesting that H2A.Z antagonizes telomeric silencing. Other Htz1-activated genes flank the silent HMR mating-type locus. Their requirement for Htz1 can be bypassed by sir2Δ or by a deletion encompassing the silencing nucleation sites in HMR. In htz1Δ cells, Sir2 and Sir3 spread into flanking euchromatic regions, producing changes in histone H4 acetylation and H3 4-methylation indicative of ectopic heterochromatin formation. Htz1 is enriched in these euchromatic regions and acts synergistically with a boundary element to prevent the spread of heterochromatin. Thus, Euchromatin and heterochromatin each contains components that antagonize switching to the opposite chromatin state.
Jasper Rine - One of the best experts on this subject based on the ideXlab platform.
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a protein complex containing the conserved swi2 snf2 related atpase swr1p deposits histone variant h2a z into Euchromatin
PLOS Biology, 2004Co-Authors: Michael S Kobor, Marc D. Meneghini, Hiten D. Madhani, Shivkumar Venkatasubrahmanyam, Jennifer L Jennings, Andrew J Link, Jasper RineAbstract:The conserved histone variant H2A.Z functions in Euchromatin to antagonize the spread of heterochromatin. The mechanism by which histone H2A is replaced by H2A.Z in the nucleosome is unknown. We identified a complex containing 13 different polypeptides associated with a soluble pool of H2A.Z in Saccharomyces cerevisiae. This complex was designated SWR1-Com in reference to the Swr1p subunit, a Swi2/Snf2-paralog. Swr1p and six other subunits were found only in SWR1-Com, whereas six other subunits were also found in the NuA4 histone acetyltransferase and/or the Ino80 chromatin remodeling complex. H2A.Z and SWR1 were essential for viability of cells lacking the EAF1 component of NuA4, pointing to a close functional connection between these two complexes. Strikingly, chromatin immunoprecipitation analysis of cells lacking Swr1p, the presumed ATPase of the complex, revealed a profound defect in the deposition of H2A.Z at euchromatic regions that flank the silent mating type cassette HMR and at 12 other chromosomal sites tested. Consistent with a specialized role for Swr1p in H2A.Z deposition, the majority of the genome-wide transcriptional defects seen in swr1Δ cells were also found in htz1Δ cells. These studies revealed a novel role for a member of the ATP-dependent chromatin remodeling enzyme family in determining the region-specific histone subunit composition of chromatin in vivo and controlling the epigenetic state of chromatin. Metazoan orthologs of Swr1p (Drosophila Domino; human SRCAP and p400) may have analogous functions.
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a protein complex containing the conserved swi2 snf2 related atpase swr1p deposits histone variant h2a z into Euchromatin
PLOS Biology, 2004Co-Authors: Michael S Kobor, Marc D. Meneghini, Hiten D. Madhani, Shivkumar Venkatasubrahmanyam, Jennifer L Jennings, Andrew J Link, Jennifer W Gin, Jasper RineAbstract:The conserved histone variant H2A.Z functions in Euchromatin to antagonize the spread of heterochromatin. The mechanism by which histone H2A is replaced by H2A.Z in the nucleosome is unknown. We identified a complex containing 13 different polypeptides associated with a soluble pool of H2A.Z in Saccharomyces cerevisiae. This complex was designated SWR1-Com in reference to the Swr1p subunit, a Swi2/Snf2-paralog. Swr1p and six other subunits were found only in SWR1-Com, whereas six other subunits were also found in the NuA4 histone acetyltransferase and/or the Ino80 chromatin remodeling complex. H2A.Z and SWR1 were essential for viability of cells lacking the EAF1 component of NuA4, pointing to a close functional connection between these two complexes. Strikingly, chromatin immunoprecipitation analysis of cells lacking Swr1p, the presumed ATPase of the complex, revealed a profound defect in the deposition of H2A.Z at euchromatic regions that flank the silent mating type cassette HMR and at 12 other chromosomal sites tested. Consistent with a specialized role for Swr1p in H2A.Z deposition, the majority of the genome-wide transcriptional defects seen in swr1Delta cells were also found in htz1Delta cells. These studies revealed a novel role for a member of the ATP-dependent chromatin remodeling enzyme family in determining the region-specific histone subunit composition of chromatin in vivo and controlling the epigenetic state of chromatin. Metazoan orthologs of Swr1p (Drosophila Domino; human SRCAP and p400) may have analogous functions.
Marc D. Meneghini - One of the best experts on this subject based on the ideXlab platform.
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a protein complex containing the conserved swi2 snf2 related atpase swr1p deposits histone variant h2a z into Euchromatin
PLOS Biology, 2004Co-Authors: Michael S Kobor, Marc D. Meneghini, Hiten D. Madhani, Shivkumar Venkatasubrahmanyam, Jennifer L Jennings, Andrew J Link, Jennifer W Gin, Jasper RineAbstract:The conserved histone variant H2A.Z functions in Euchromatin to antagonize the spread of heterochromatin. The mechanism by which histone H2A is replaced by H2A.Z in the nucleosome is unknown. We identified a complex containing 13 different polypeptides associated with a soluble pool of H2A.Z in Saccharomyces cerevisiae. This complex was designated SWR1-Com in reference to the Swr1p subunit, a Swi2/Snf2-paralog. Swr1p and six other subunits were found only in SWR1-Com, whereas six other subunits were also found in the NuA4 histone acetyltransferase and/or the Ino80 chromatin remodeling complex. H2A.Z and SWR1 were essential for viability of cells lacking the EAF1 component of NuA4, pointing to a close functional connection between these two complexes. Strikingly, chromatin immunoprecipitation analysis of cells lacking Swr1p, the presumed ATPase of the complex, revealed a profound defect in the deposition of H2A.Z at euchromatic regions that flank the silent mating type cassette HMR and at 12 other chromosomal sites tested. Consistent with a specialized role for Swr1p in H2A.Z deposition, the majority of the genome-wide transcriptional defects seen in swr1Delta cells were also found in htz1Delta cells. These studies revealed a novel role for a member of the ATP-dependent chromatin remodeling enzyme family in determining the region-specific histone subunit composition of chromatin in vivo and controlling the epigenetic state of chromatin. Metazoan orthologs of Swr1p (Drosophila Domino; human SRCAP and p400) may have analogous functions.
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a protein complex containing the conserved swi2 snf2 related atpase swr1p deposits histone variant h2a z into Euchromatin
PLOS Biology, 2004Co-Authors: Michael S Kobor, Marc D. Meneghini, Hiten D. Madhani, Shivkumar Venkatasubrahmanyam, Jennifer L Jennings, Andrew J Link, Jasper RineAbstract:The conserved histone variant H2A.Z functions in Euchromatin to antagonize the spread of heterochromatin. The mechanism by which histone H2A is replaced by H2A.Z in the nucleosome is unknown. We identified a complex containing 13 different polypeptides associated with a soluble pool of H2A.Z in Saccharomyces cerevisiae. This complex was designated SWR1-Com in reference to the Swr1p subunit, a Swi2/Snf2-paralog. Swr1p and six other subunits were found only in SWR1-Com, whereas six other subunits were also found in the NuA4 histone acetyltransferase and/or the Ino80 chromatin remodeling complex. H2A.Z and SWR1 were essential for viability of cells lacking the EAF1 component of NuA4, pointing to a close functional connection between these two complexes. Strikingly, chromatin immunoprecipitation analysis of cells lacking Swr1p, the presumed ATPase of the complex, revealed a profound defect in the deposition of H2A.Z at euchromatic regions that flank the silent mating type cassette HMR and at 12 other chromosomal sites tested. Consistent with a specialized role for Swr1p in H2A.Z deposition, the majority of the genome-wide transcriptional defects seen in swr1Δ cells were also found in htz1Δ cells. These studies revealed a novel role for a member of the ATP-dependent chromatin remodeling enzyme family in determining the region-specific histone subunit composition of chromatin in vivo and controlling the epigenetic state of chromatin. Metazoan orthologs of Swr1p (Drosophila Domino; human SRCAP and p400) may have analogous functions.
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Conserved Histone Variant H2A.Z Protects Euchromatin from the Ectopic Spread of Silent Heterochromatin
Cell, 2003Co-Authors: Marc D. Meneghini, Hiten D. MadhaniAbstract:Boundary elements hinder the spread of heterochromatin, yet these sites do not fully account for the preservation of adjacent Euchromatin. Histone variant H2A.Z (Htz1 in yeast) replaces conventional H2A in many nucleosomes. Microarray analysis revealed that HTZ1-activated genes cluster near telomeres. The reduced expression of most of these genes in htz1Δ cells was reversed by the deletion of SIR2 (sir2Δ) suggesting that H2A.Z antagonizes telomeric silencing. Other Htz1-activated genes flank the silent HMR mating-type locus. Their requirement for Htz1 can be bypassed by sir2Δ or by a deletion encompassing the silencing nucleation sites in HMR. In htz1Δ cells, Sir2 and Sir3 spread into flanking euchromatic regions, producing changes in histone H4 acetylation and H3 4-methylation indicative of ectopic heterochromatin formation. Htz1 is enriched in these euchromatic regions and acts synergistically with a boundary element to prevent the spread of heterochromatin. Thus, Euchromatin and heterochromatin each contains components that antagonize switching to the opposite chromatin state.