Five SWI/SNF gene products are components of a large multisubunit complex required for transcriptional enhancement.

The Saccharomyces cerevisiae SWI1, SWI2 (SNF2), SWI3, SNF5, and SNF6 gene products play a crucial role in the regulation of transcription. We provide here direct biochemical evidence that all five 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 approximately 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 APT-binding site of SWI2, although this mutation eliminates SWI2 function.