5 SWI/SNF GENE-PRODUCTS ARE COMPONENTS OF A LARGE MULTISUBUNIT COMPLEX REQUIRED FOR TRANSCRIPTIONAL ENHANCEMENT

The Saccharomyces cerevisiae SW11, SWI2 (SNF2), SWI3, SNFS, and SNF6 gene products play a crucial role in the regulation of transcription. We provide here direct biochemical evidence that all rive SWI/SNF polypeptides are components of a large multisubunit complex. These five polypeptides coelute from a gel-filtration column with an apparent molecular mass of almost-equal-to 2 MDa. The five SWI/SNF polypeptides do not copurify when extracts are prepared from swi- or snf- mutants. We show that SWI/SNF polypeptides also remain associated during an affinity-chromatography step followed by gel filtration. Assembly of the SWI/SNF complex is not disrupted by a mutation in the putative ATP-binding site of SWI2, although this mutation eliminates SWI2 function.