Histone H3 lysine 36 methylation antagonizes silencing in Saccharomyces cerevisiae independently of the Rpd3S histone deacetylase complex.
In yeast, methylation of histone H3 on lysine 36 (H3-K36) is catalyzed by the NSD1 leukemia oncoprotein homolog Set2. The histone deacetylase complex Rpd3S is recruited to chromatin via binding of the chromodomain protein Eaf3 to methylated H3-K36 to prevent erroneous transcription initiation. Here we identify a distinct function for H3-K36 methylation. We used random mutagenesis of histones H3 and H4 followed by a reporter-based screen to identify residues necessary to prevent the ectopic spread of silencing from the silent mating-type locus HMRa into flanking euchromatin. Mutations in H3-K36 or deletion of SET2 caused ectopic silencing of a heterochromatin-adjacent reporter. Transcriptional profiling revealed that telomere-proximal genes are enriched for those that display decreased expression in a set2Delta strain. Deletion of SIR4 rescued the expression defect of 26 of 37 telomere-proximal genes with reduced expression in set2Delta cells, implying that H3-K36 methylation prevents the spread of telomeric silencing. Indeed, Sir3 spreads from heterochromatin into neighboring euchromatin in set2Delta cells. Furthermore, genetic experiments demonstrated that cells lacking the Rpd3S-specific subunits Eaf3 or Rco1 did not display the anti-silencing phenotype of mutations in SET2 or H3-K36. Thus, antagonism of silencing is independent of the only known effector of this conserved histone modification.
Tompa
Rachel
R
Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143-2200, USA.
Madhani
Hiten D
HD
D022041:Euchromatin / Q000378:metabolism; D020868:Gene Silencing; D005799:Genes, Dominant; D049770:Genes, Mating Type, Fungal; D005820:Genetic Testing; D006655:Histone Deacetylases / Q000378:metabolism*; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism*; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000378:metabolism; D016615:Telomere / Q000378:metabolism
D022041:Euchromatin; D006657:Histones; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D008780:Methyltransferases; C448996:Set2 protein, S cerevisiae; C416235:Dot1 protein, S cerevisiae; D011495:Histone-Lysine N-Methyltransferase; C071665:RPD3 protein, S cerevisiae; D006655:Histone Deacetylases; D008239:Lysine