Sas3 and Ada2(Gcn5)-dependent histone H3 acetylation is required for transcription elongation at the de-repressed FLO1 gene.

Michael Church,Sari Pennings,Kim C Smith,Alastair B Fleming,Mohamed M Alhussain

doi:10.1093/nar/gkx028

Abstract

The Saccharomyces cerevisiae FLO1 gene encodes a cell wall protein that imparts cell–cell adhesion. FLO1 transcription is regulated via the antagonistic activities of the Tup1–Cyc8 co-repressor and Swi–Snf co-activator complexes. Tup1–Cyc8 represses transcription through the organization of strongly positioned, hypoacetylated nucleosomes across gene promoters. Swi–Snf catalyzes remodeling of these nucleosomes in a mechanism involving histone acetylation that is poorly understood. Here, we show that FLO1 de-repression is accompanied by Swi–Snf recruitment, promoter histone eviction and Sas3 and Ada2(Gcn5)-dependent histone H3K14 acetylation. In the absence of H3K14 acetylation, Swi–Snf recruitment and histone eviction proceed, but transcription is reduced, suggesting these processes, while essential, are not sufficient for de-repression. Further analysis in the absence of H3K14 acetylation reveals RNAP II recruitment at the FLO1 promoter still occurs, but RNAP II is absent from the gene-coding region, demonstrating Sas3 and Ada2-dependent histone H3 acetylation is required for transcription elongation. Analysis of the transcription kinetics at other genes reveals shared mechanisms coupled to a distinct role for histone H3 acetylation, essential at FLO1, downstream of initiation. We propose histone H3 acetylation in the coding region provides rate-limiting control during the transition from initiation to elongation which dictates whether the gene is permissive for transcription.

Highlights

The yeast FLO1 gene encodes a lectin-like cell wall protein, which promotes non-sexual, calcium-dependent cell aggregation observable as a flocculation phenotype [1,2,3]
We discovered that Ada2 and Sas3 are not required for RNA polymerase II (RNAP II) recruitment to the FLO1 promoter but occupancy of RNAP II in the FLO1 open reading frame (ORF) is Ada2(Gcn5) and Sas3-dependent
We have identified that the Sas3 and Gcn5containing histone acetyltransferases (HATs) complexes are required for FLO1 derepression in the absence of Cyc8 and that this role is mediated via histone H3K14 acetylation at the FLO1 promoter and ORF (Figure 8D)

Summary

Introduction

The yeast FLO1 gene encodes a lectin-like cell wall protein, which promotes non-sexual, calcium-dependent cell aggregation observable as a flocculation phenotype [1,2,3]. Flocculation provides cell populations with a survival strategy against external stresses whereby cells within the ‘floc’ are physically shielded from the outside environment [5]. Flocculation has been shown to enhance cell mating [6]. Flocculation is an important phenotype by which populations of cells collaborate to aid their mutual survival. This phenotype is important in biofilm formation, and in industries such as brewing where it aids in the removal of yeast cells after fermentation [7,8]

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