SNF11, a New Component of the Yeast SNF-SWI Complex That Interacts with a Conserved Region of SNF2

Abstract

The yeast SNF-SWI complex is required for transcriptional activation of diverse genes and has been shown to alter chromatin structure. The complex has at least 10 components, including SNF2/SWI2, SNF5, SNF6, SWI1/ADR6, and SWI3, and has been widely conserved in eukaryotes. Here we report the characterization of a new component. We identified proteins that interact in the two-hybrid system with the N-terminal region of SNF2, preceding the ATPase domain. In addition to SWI3, we recovered a new 19-kDa protein, designated SNF11. Like other SNF/SWI proteins, SNF11 functions as a transcriptional activator in genetic assays. SNF11 interacts with SNF2 in vitro and copurifies with the SNF-SWI complex from yeast cells. Using a specific antibody, we showed that SNF11 coimmunoprecipitates with members of the SNF-SWI complex and that SNF11 is tightly and stoichiometrically associated with the complex. Furthermore, SNF11 was detected in purified SNF-SWI complex by staining with Coomassie blue dye; its presence previously went unrecognized because it does not stain with silver. SNF11 interacts with a 40-residue sequence of SNF2 that is highly conserved, suggesting that SNF11 homologs exist in other organisms.Transcriptional control involves a complex interplay between gene-specific activators, the general transcription apparatus, and chromatin. The SNF-SWI complex has an important role in this process in the yeast Saccharomyces cerevisiae. The SNF-SWI complex is required for transcriptional activation of an array of differently regulated genes (for a review, see reference 4) and has been shown to alter chromatin structure to facilitate binding of transcription factors (7,15). Components of this complex include SNF2/SWI2, SNF5, SNF6, SWI1/ ADR6, SWI3, and at least five additional polypeptides (3,7,35). This complex has been widely conserved in eukaryotes. Proteins homologous to several components have been identified in Drosophila melanogaster and mammals, and a similar complex has been purified from humans (20).The yeast SNF and SWI genes were originally identified by mutations that affect SUC2 expression (snf) and mating-type switching (swi) (30,41). Subsequent genetic studies implicated these genes in transcription of diversely regulated promoters (1,10,13,23,32,36). A role in transcriptional activation was suggested by evidence that each of the SNF proteins, when artificially bound to DNA as a LexA fusion, activates transcription of a target gene (23,24). Moreover, SNF and SWI proteins enhance transcriptional activation by various gene-specific activators expressed in S. cerevisiae, including GAL4, LexA-GAL4, LexA-Bicoid, Drosophila fushi tarazu, and rat glucocorticoid receptor (21,36,46).Genetic evidence first suggested that SNF/SWI proteins affect transcriptional activation by relieving repressive effects of chromatin (for a review, see reference 45). Transcriptional defects of snf/swi mutants are suppressed by mutations in histone genes and genes encoding other chromatin-related proteins (15,19,31,37,42). In addition, in...

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