ausblenden:
Schlagwörter:
Alanine/genetics/metabolism
Amino Acid Motifs
Amino Acid Sequence
Binding Sites
Cell Nucleolus/metabolism
Chromatin/genetics
Chromosomal Proteins, Non-Histone/metabolism
DNA, Ribosomal/genetics
Epistasis, Genetic
Glutamine/*metabolism
Histones/*chemistry/*metabolism
Humans
Methylation
Methyltransferases/metabolism
Molecular Chaperones/metabolism
Molecular Sequence Data
Multiprotein Complexes/metabolism
Nuclear Proteins/metabolism
Nucleosomes/metabolism
Protein Binding
Protein Processing, Post-Translational
RNA/metabolism
RNA Polymerase I/*metabolism
Ribonucleoproteins, Small Nucleolar/metabolism
Saccharomyces cerevisiae/enzymology/genetics/metabolism
Saccharomyces cerevisiae Proteins/metabolism
Substrate Specificity
Transcription, Genetic
Zusammenfassung:
Nucleosomes are decorated with numerous post-translational modifications capable of influencing many DNA processes. Here we describe a new class of histone modification, methylation of glutamine, occurring on yeast histone H2A at position 105 (Q105) and human H2A at Q104. We identify Nop1 as the methyltransferase in yeast and demonstrate that fibrillarin is the orthologue enzyme in human cells. Glutamine methylation of H2A is restricted to the nucleolus. Global analysis in yeast, using an H2AQ105me-specific antibody, shows that this modification is exclusively enriched over the 35S ribosomal DNA transcriptional unit. We show that the Q105 residue is part of the binding site for the histone chaperone FACT (facilitator of chromatin transcription) complex. Methylation of Q105 or its substitution to alanine disrupts binding to FACT in vitro. A yeast strain mutated at Q105 shows reduced histone incorporation and increased transcription at the ribosomal DNA locus. These features are phenocopied by mutations in FACT complex components. Together these data identify glutamine methylation of H2A as the first histone epigenetic mark dedicated to a specific RNA polymerase and define its function as a regulator of FACT interaction with nucleosomes.
