Silencing Proteins Sir3 and Sir4 have Distinct Roles in the Assembly of Silent Chromatin in Budding Yeast

• Main Author: Harding, Katherine
• Other Authors: Rudner, Adam
• Format: Others
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2014
• Subjects: SIR proteins; Budding Yeast
• Online Access: http://hdl.handle.net/10393/31578; http://dx.doi.org/10.20381/ruor-4049

The Silent Information Regulator (SIR) complex is responsible for the formation of silent chromatin domains in Saccharomyces cerevisiae, and consists of the NAD-dependent histone deacetylase Sir2, and histone binding proteins Sir3 and Sir4. The current model of silent chromatin assembly proposes that histone deacetylation by Sir2 is required to promote recruitment of Sir3 and Sir4, and assembly of full SIR complexes on chromatin. However, recent work has suggested unique roles for the histone binding proteins Sir3 and Sir4 in this process. Here we present data suggesting that Sir3 is primarily responsible for mediating the spreading of silent chromatin from sites of nucleation, while regulation of Sir4 abundance controls the rate of silencing establishment. We have also investigated a potential novel dimerization domain in Sir3, which may represent a conserved function in vertebrates. Investigations into the regulation of silent chromatin assembly in budding yeast will facilitate our understanding of the mechanisms that control heterochromatin-mediated gene repression in higher organisms.