Genome-wide Analysis of Functional Sirtuin Chromatin Targets in Yeast

Sir2 and the homologous proteins, Hst1, Hst2, Hst3, and Hst4 from Saccharomyces cerevisiae are NAD+-dependent histone deacetylases of the sirtuin protein family. Sir2 functions in transcriptional silencing at the silent mating-type loci, telomeres, and rDNA locus, but also promotes replicative lifespan. To gain a better understanding of the chromatin-regulatory roles carried out by Sir2 and the Hst proteins, we performed ChIP-sequencing analysis on all five sirtuins and Sum1, the DNA binding partner for Hst1. Sir2, Hst1, and Sum1 were abundantly, and functionally co-enriched at several major targets, including the telomeric repeats, where they were required for maintaining proper telomere repeat length. At tRNA target genes they were required for efficient cohesin and condensin deposition. Across the open reading frames of glycolytic and ribosomal protein genes, Sir2 and Hst1 functioned in NAD+-dependent transcriptional repression at the diauxic shift, directly linking Sir2 to glucose metabolism, which could have implications for longevity.