FUNCTIONAL-ANALYSIS OF THE DNA-STIMULATED ATPASE DOMAIN OF YEAST SW12SNF2/

The yeast SWI2/SNF2 polypeptide is a subunit of the SWI/SNF protein co mplex that is required for many transcriptional activators to function in a chromatin context, SWI2 is believed to be the founding member of a new subfamily of DNA-stimulated ATPases/DNA helicases that includes proteins that function in DNA repair (RAD5, RAD16, ERCC6), recombinat ion (RAD54), transcription (MOT1, ISWI, brm, BRG1, hBRM) and cell cycl e control (STH1), We have created a set of 16 mutations within the SWI 2 ATPase domain and have analyzed the functional consequences of these mutations in vivo. We have identified residues within each of the sev en ATPase motifs that are required for SWI2 function, We have also ide ntified crucial residues that are interspersed between the known ATPas e motifs, In contrast, we identify other highly conserved residues tha t appear to be dispensable for SWI2 function, We also find that single amino acid changes in ATPase motifs IV and VI lead to a dominant nega tive phenotype, None of the 12 SWI2 mutations that disrupt SWI2 activi ty in vivo alter the assembly of the SWI/SNF complex, These studies pr ovide an invaluable framework for biochemical analysis of the SWI2 ATP ase and for functional analysis of other SWI2 family members.