title: Distinct roles for the essential MYST family HAT Esa1p in transcriptional silencing.
abstract: Among acetyltransferases, the MYST family enzyme Esa1p is distinguished for its essential function and contribution to transcriptional activation and DNA double-stranded break repair. Here we report that Esa1p also plays a key role in silencing RNA polymerase II (Pol II)-transcribed genes at telomeres and within the ribosomal DNA (rDNA) of the nucleolus. These effects are mediated through Esa1p's HAT activity and correlate with changes within the nucleolus. Esa1p is enriched within the rDNA, as is the NAD-dependent protein deacetylase Sir2p, and the acetylation levels of key Esa1p histone targets are reduced in the rDNA in esa1 mutants. Although mutants of both ESA1 and SIR2 have enhanced rates of rDNA recombination, esa1 effects are more modest yet result in distinct structural changes of rDNA chromatin. Surprisingly, increased expression of ESA1 can bypass the requirement for Sir2p in rDNA silencing, suggesting that these two enzymes with seemingly opposing activities both contribute to achieve optimal nucleolar chromatin structure and function.
authors.affiliation: Division of Biological Sciences, UCSD Cancer Center and Center for Molecular Genetics, University of California-San Diego, La Jolla, CA 92093, USA.
authors.forename: Astrid S
authors.initials: AS
authors.lastname: Clarke
authors.forename: Eva
authors.initials: E
authors.lastname: Samal
authors.forename: Lorraine
authors.initials: L
authors.lastname: Pillus
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry / Q000201:enzymology; D002843:Chromatin / Q000378:metabolism; D015825:Chromosomes, Fungal / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics* / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics* / Q000378:metabolism; D018628:Gene Dosage; D020868:Gene Silencing; D051548:Histone Acetyltransferases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D056565:Sirtuin 2; D037761:Sirtuins / Q000235:genetics / Q000378:metabolism; D020080:Tandem Repeat Sequences; D016615:Telomere / Q000201:enzymology; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C496551:Esa1 protein, S cerevisiae; D051548:Histone Acetyltransferases; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases