Promoter regulation by distinct mechanisms of functional interplay between lysine acetylase Rtt109 and histone chaperone Asf1.

The promoter activity of yeast genes can depend on lysine 56 (K56) acetylation of histone H3. This modification of H3 is performed by lysine acetylase Rtt109 acting in concert with histone chaperone Asf1. We have examined the contributions of Rtt109, Asf1, and H3 K56 acetylation to nutrient regulation of a well-studied metabolic gene, ARG1.

SWI/SNF and Asf1 independently promote derepression of the DNA damage response genes under conditions of replication stress.

The histone chaperone Asf1 and the chromatin remodeler SWI/SNF have been separately implicated in derepression of the DNA damage response (DDR) genes in yeast cells treated with genotoxins that cause replication interference. Using genetic and biochemical approaches, we have tested if derepression of the DDR genes in budding yeast involves functional interplay between Asf1 and SWI/SNF. We find that Asf1 and SWI/SNF are both recruited to DDR genes under replication stress triggered by hydroxyurea, and have detected a soluble complex that contains Asf1 and the Snf2 subunit of SWI/SNF.

Asf1 can promote trimethylation of H3 K36 by Set2.

Asf1 is a conserved histone H3/H4 chaperone that can assemble and disassemble nucleosomes and promote histone acetylation. Set2 is an H3 K36 methyltransferase. The functions of these proteins intersect in the context of transcription elongation by RNA polymerase II: both contribute to the establishment of repressive chromatin structures that inhibit spurious intragenic transcription.