Project description:Dynamic modification of the carboxy-terminal domain (CTD) of RNA polymerase II (RNAPII) regulates transcription-coupled processes in eukaryotes. The CTD in mammals is composed of 52 heptad-repeats with the consensus sequence Y1-S2-P3-T4-S5-P6-S7. Repeats in the distal part of CTD deviate from the consensus sequence and have frequently replaced serine at position 7 by lysine residues (K7). Mass spectrometry analysis revealed modification of K7 residues in heptad-repeats 39, 42, and 47/49 by acetylation and in heptad-repeats 38, 39, 40, 42, and 47/49 by mono-, di-, or trimethylation. Notably, acetylated as well as di- and tri-methylated K7 residues were found exclusively in phosphorylated CTD peptides, while mono-methylated K7 residues occurred also in non-phosphorylated CTD peptides. Methylation of K7 residues was further studied with the monoclonal antibody (mAb) 1F5, which recognizes mono- and di-methylated K7 in CTD. ChIP experiments revealed high levels of K7 methylation at the transcriptional start site of genes. The low levels of K7 methylation in the body of genes results from impairment of epitope recognition in hyper-phosphorylated CTD by mAb 1F5. In agreement with this notion, phosphatase treatment of hyper-phosphorylated CTD or treatment of cells with kinase inhibitor flavopiridol restored the reactivity of mAb 1F5 towards methylated K7 residues in CTD. We conclude that methylation and acetylation of K7 residues further expand the mammalian CTD code and potentially contribute to regulation of gene expression.
Project description:Dynamic post-translational modification of RNA polymerase II (RNAPII) coordinates the co-transcriptional recruitment of enzymatic complexes that regulate chromatin states and co-transcriptional processing of nascent RNA. Extensive phosphorylation of serine residues occurs at the structurally-disordered C-terminal domain (CTD) of the largest RNAPII subunit, which is composed of multiple heptapeptide repeats with consensus sequence Y1-S2-P3-T4-S5-P6-S7. Serine-5 and Serine-7 phosphorylation mark transcription initiation, whereas Serine-2 phosphorylation coincides with productive elongation. In vertebrates, the CTD has eight non-canonical substitutions of Serine-7 into Lysine-7, which can be acetylated (K7ac). Here, we describe for the first time mono- and di-methylation of CTD Lysine-7 residues (K7me1 and K7me2). K7me1 and K7me2 are observed during the earliest transcription stages and precede or accompany Serine-5 and Serine-7 phosphorylation. Genome wide mapping of 2 novel RNAPII post-translational modifications (CTD-K7me1 and CTD-K7me2) in mouse ES cells.
Project description:We have performed a comprehensive analysis of the involvement of histone H3 and H4 residues in the regulation of chronological lifespan in yeast. Residues where substitution resulted in the most pronounced lifespan extension are all on the exposed face of the nucleosome, with the exception of H3E50, which is present on the lateral surface, between two DNA gyres. Other residues that had a more modest effect on lifespan extension were concentrated at the extremities of the H3-H4 dimer, suggesting a role in stabilizing the dimer in its nucleosome frame. Residues implicated in a reduced lifespan were buried in the histone handshake motif, suggesting that these mutations destabilize the octamer structure. All residues exposed on the disk and that caused lifespan extension are known to interact with Sir3. We find that substitution of H4K16 and H4H18 cause Sir3 to redistribute from telomeres and silent mating loci to secondary positions, often enriched for Rap1 or Abf1 binding sites, whereas H3E50 does not. The redistributed Sir3 cause transcriptional repression at most of the new loci, including of genes where null mutants were previously shown to extend chronological lifespan. The transcriptomic profiles of H4K16 and H4H18 mutant strains are very similar, and compatible with a DNA replication stress response. This is distinct from the transcriptomic profile of H3E50, which matches strong induction of oxidative phosphorylation. We propose that different clusters of H3 and H4 residues are involved in either binding to non-histone proteins, or in destabilizing the association of the nucleosome DNA, or disrupting binding of a H3-H4 dimer in the nucleosome, or disturbing the structural stability of the octamer, each category impacting on chronological lifespan through a different path.
Project description:We have performed a comprehensive analysis of the involvement of histone H3 and H4 residues in the regulation of chronological lifespan in yeast. Residues where substitution resulted in the most pronounced lifespan extension are all on the exposed face of the nucleosome, with the exception of H3E50, which is present on the lateral surface, between two DNA gyres. Other residues that had a more modest effect on lifespan extension were concentrated at the extremities of the H3-H4 dimer, suggesting a role in stabilizing the dimer in its nucleosome frame. Residues implicated in a reduced lifespan were buried in the histone handshake motif, suggesting that these mutations destabilize the octamer structure. All residues exposed on the disk and that caused lifespan extension are known to interact with Sir3. We find that substitution of H4K16 and H4H18 cause Sir3 to redistribute from telomeres and silent mating loci to secondary positions, often enriched for Rap1 or Abf1 binding sites, whereas H3E50 does not. The redistributed Sir3 cause transcriptional repression at most of the new loci, including of genes where null mutants were previously shown to extend chronological lifespan. The transcriptomic profiles of H4K16 and H4H18 mutant strains are very similar, and compatible with a DNA replication stress response. This is distinct from the transcriptomic profile of H3E50, which matches strong induction of oxidative phosphorylation. We propose that different clusters of H3 and H4 residues are involved in either binding to non-histone proteins, or in destabilizing the association of the nucleosome DNA, or disrupting binding of a H3-H4 dimer in the nucleosome, or disturbing the structural stability of the octamer, each category impacting on chronological lifespan through a different path.
Project description:The functions of MYC acetylation have remained unclear. In this study we identified the major lysine residues of MYC that are acetylated by p300 and GCN5 in cancer cell lines and established the requirment of three specific acetyl-lysine (AcK) residues for MYC transformation of Rat1a fibroblasts and MCF10 mammary epithelial cells. We further uncovered gene-selective regulatory functions and conserved genetic programs and biolofical processes regulated by MYC AcK residues in both cell types.
Project description:The functions of MYC acetylation have remained unclear. In this study we identified the major lysine residues of MYC that are acetylated by p300 and GCN5 in cancer cell lines and established the requirment of three specific acetyl-lysine (AcK) residues for MYC transformation of Rat1a fibroblasts and MCF10 mammary epithelial cells. We further uncovered gene-selective regulatory functions and conserved genetic programs and biolofical processes regulated by MYC AcK residues in both cell types.