ESSENTIAL ROLE OF SWP73P IN THE FUNCTION OF YEAST SWI SNF COMPLEX/

Swi/Snf protein was purified previously from the yeast Saccharomyces c erevisiae as an 11-polypeptide complex, including five novel Swp polyp eptides. Here we present evidence concerning the role of Swp73p in the function of the complex. Deletion mutants in the SWP73 gene display p henotypes similar to those of swi and snf mutants, and in addition are temperature-sensitive. Swp73p is required for transcriptional activat ion by full-length glucocorticoid receptor (GR), but not by all GR der ivatives. Swp73p is also required for activation with an enhancer elem ent that binds the transcription factors Swi5p and Pho2p, which may un derlie the defects in HO expression observed with swi and snf mutants. A single amino acid change in the protein confers phenotypes that are similar to those observed in the swp 73 Delta strain, but in some cas es the two strains behave differently. The extent to which Swp73p is r equired for assisting transcriptional activation depends on the activa tor and promoter tested. Homologs of SWP73 are present in S. cerevisia e, Ashbya gossypii, Caenorhabditis elegans, and mice, indicating that SWP73 may belong to a family of related genes encoding proteins with a nalogous functions.