Open AccessStructure and Function of the Saccharomyces cerevisiae Sir3 BAH Domain
Author(s) -
Jessica J. Connelly,
Peihua Yuan,
Hao-Chi Hsu,
Zhizhong Li,
Rui-Ming Xu,
Rolf Sternglanz
Publication year - 2006
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.26.8.3256-3265.2006
Subject(s) - biology , saccharomyces cerevisiae , gene silencing , genetics , superhelix , microbiology and biotechnology , dna , gene , dna replication , dna supercoil
Previous work has shown that the N terminus of theSaccharomyces cerevisiae Sir3 protein is crucial for the function of Sir3 in transcriptional silencing. Here, we show that overexpression of N-terminal fragments of Sir3 in strains lacking the full-length protein can lead to some silencing ofHML andHMR . Sir3 contains a BAH (bromo-adjacent homology) domain at its N terminus. Overexpression of this domain alone can lead to silencing as long as Sir1 is overexpressed and Sir2 and Sir4 are present. Overexpression of the closely related Orc1 BAH domain can also silence in the absence of any Sir3 protein. A previously characterized hypermorphicsir3 mutation, D205N, greatly improves silencing by the Sir3 BAH domain and allows it to bind to DNA and oligonucleosomes in vitro. A previously uncharacterized region in the Sir1 N terminus is required for silencing by both the Sir3 and Orc1 BAH domains. The structure of the Sir3 BAH domain has been determined. In the crystal, the molecule multimerizes in the form of a left-handed superhelix. This superhelix may be relevant to the function of the BAH domain of Sir3 in silencing.