Involved in transcriptional activation. Component of the SWI/SNF complex, an ATP-dependent chromatin remodeling complex, which is required for the positive and negative regulation of gene expression of a large number of genes. It changes chromatin structure by altering DNA-histone contacts within a nucleosome, leading eventually to a change in nucleosome position, thus facilitating or repressing binding of gene-specific transcription factors. Component of the SWI/SNF global transcription activator complex. The 1.14 MDa SWI/SNF complex is composed of 11 different subunits: one copy each of SWI1, SNF2/SWI2, SNF5, SNF12/SWP73, ARP7/SWP61, ARP9/SWP59; two copies each of SWI3, SNF6, SNF11, SWP82; and three copies of TAF14/SWP29. While the soluble protein is nuclear, [SWI+] aggregates appear to be cytoplasmic. The prion domain (PrD) is a Gln/Asn (Q/N)-rich domain, which is unstructured in its native, soluble form, and which forms a parallel in-register beta-sheet in its amyloid form (By similarity). The first 37 residues of this domain are sufficient for aggregation, propagation, and transmission of the [SWI+] prion. [SWI+] is the prion form of SWI1 (PubMed:18362884). [SWI+] is the result of a conformational change of the cellular SWI1 protein that becomes self-propagating and infectious. This conformational change generates a form of SWI1 that assembles into amyloid fibrils (PubMed:20679490). [SWI+]-aggregates sequester soluble SWI1, resulting in reduced growth on carbon sources other than glucose, reminiscent of a partial loss of function of the SWI/SNF chromatin-remodeling complex. [SWI+] can be cured by GdnHCl and by deletion of the molecular chaperone HSP104, which is required for [SWI+] propagation (PubMed:18362884). [SWI+] propagation is highly dependent upon the action of members of the Hsp70 molecular chaperone system, specifically the Hsp70 SSA, two of its J-protein co-chaperones, SIS1 and YDJ1, and the nucleotide exchange factors of the Hsp110 family (SSE1/2). Both under- and overexpression of components of this system initiate rapid loss of the prion from the cell population. It is speculated that prion properties of transcription factors may generate an optimized phenotypic heterogeneity that buffers yeast populations against diverse environmental insults (PubMed:21379326). Present with 92 molecules/cell in log phase SD medium. Belongs to the SWI1 family.