The C-Terminal Domain of Sin1 Interacts with the SWI-SNF Complex in Yeast

ABSTRACT

In the yeast Saccharomyces cerevisiae, the SWI-SNF complex has been proposed to antagonize the repressive effects of chromatin by disrupting nucleosomes. The SIN genes were identified as suppressors of defects in the SWI-SNF complex, and the SIN1 gene encodes an HMG1-like protein that has been proposed to be a component of chromatin. Specific mutations (sin mutations) in both histone H3 and H4 genes produce the same phenotypic effects as do mutations in the SIN1 gene. In this study, we demonstrate that Sin1 and the H3 and H4 histones interact genetically and that the C terminus of Sin1 physically associates with components of the SWI-SNF complex. In addition, we demonstrate that this interaction is blocked in the full-length Sin1 protein by the N-terminal half of the protein. Based on these and additional results, we propose that Sin1 acts as a regulatable bridge between the SWI-SNF complex and the nucleosome.

ACKNOWLEDGMENTS

We thank R. K. Tabtiang for providing indispensable strains, plasmids, antibodies, and advice throughout the course of this work; E. T. Young for providing anti-SWI1 antibodies; B. Cairns for providing anti-SNF6 and anti-SWP73 antibodies; D. Moazed for expert advice on affinity purification procedures; R. Smith for proposing the experiment shown in Fig. 6A; and B. Braun, I. Herskowitz, D. Moazed, R. K. Tabtiang, and F. Winston for comments on the manuscript.

This study was supported by an NIH grant to A.D.J. and an EMBO long-term postdoctoral fellowship to J.P.-M.