The yeastSIN3 gene functions as a transcriptional repressor, despite the fact that Sin3p does not bind DNA directly. We have conducted a two-hybrid screen to look for proteins that interact with Sin3p, using the PAH2 domain of Sin3p as bait. Five new genes,STB1–STB5 were identified, as well as theSTB6 gene, which is similar toSTB2.STB1,STB2,STB3, andSTB6 are novel genes, andSTB4 andSTB5 encode C6 zinc cluster DNA-binding proteins. None of these genes is essential for viability, and several of these genes may encode transcriptional activators. Several special problems were encountered in using a transcriptional repressor in a two-hybrid screen. For example, theSTB genes will interact with a LexA-Sin3(PAH2) fusion protein containing a region of Sin3p, but a LexA-Sin3p fusion protein containing full-length Sin3p, along with aSTB clone, does not produce two-hybrid activation of a transcriptional reporter. In addition, asin3 mutation reduces the transcriptional activation by two-hybrid partners, suggesting that asin3 mutation reduces the transcriptional efficiency of the Gal4p and VP16 activation domains. We have shown previously that Sin3p is part of a large multiprotein complex, and we show here that Stb1p and Stb2p are present in this complex.

Authors and Affiliations

1. Division of Molecular Biology and Genetics, Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA Fax: + 1–801–581–3607; e-mail: stillman@genetics.utah.edu, , , , , , US

   M. M. Kasten & D. J. Stillman

Received: 2 April 1997 / Accepted: 2 July 1997

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