The roles of DNA and @entity32350 interactions in determining the overlapping and distinct functions of the @entity375 cell cycle regulatory transcription factors @entity23470 and @entity23471 were examined. Full-length recombinant @entity23470 and @entity23471 were purified and their binding to bona fide promoters examined in vitro. Each protein bound a variety of target promoters with similar specificity in vitro, consistent with the observation that these proteins bind common promoters in vivo. However, in vivo, the @entity23470 and @entity23471 occupied different target promoters to different extents, suggesting that each was primarily responsible for controlling a different set of genes. Additional in vitro studies provided a mechanistic explanation for this differential promoter-occupancy. Specifically, the @entity23471 , but not the @entity23470 , was capable of binding cooperatively with @entity32350 . The @entity32350 - @entity23471 cooperative binding was enhanced by, but did not require, the presence of a @entity32350 -binding site within a target promoter. Consistent with these data, @entity32350 was present at Fkh-controlled promoters in vivo regardless of whether they contained @entity32350 -binding sites, suggesting a role for @entity32350 at promoters not thought previously to be under @entity32350 control. Analysis of @entity23470 and @entity23471 binding to promoter targets in vivo by use of mutant strains indicated that the two proteins compete for promoter-occupancy at a number of target promoters. We postulate that @entity23470 and a stable @entity23471 / @entity32350 complex compete for binding to target promoters and that the levels and/or binding activity of @entity23470 , but not @entity23471 , are most limiting for promoter-occupancy in vivo. Interestingly, the in vitro DNA-binding assays, using a variety of promoter targets, revealed that bona fide Fkh target promoters contained two or more Fkh-binding sites that allowed the @entity23470 and @entity23471 proteins to form multiple protein-DNA complexes in vitro. Multiple Fkh-binding sites may be a distinguishing feature of bona fide Fkh promoters in @entity375 and other organisms.

Mechanisms controlling differential promoter-occupancy by the @entity375 forkhead proteins XXXX and @entity23471 : implications for regulating the cell cycle and differentiation.

@entity32350 :: ('855060(Tax:4932)', 'Gene') :: ['Mcm1p'] @entity23470 :: ('854675(Tax:4932)', 'Gene') :: ['Fkh1p'] @entity375 :: ('4932', 'Species') :: ['yeast'] @entity23471 :: ('855656(Tax:4932)', 'Gene') :: ['Fkh2p']
@entity23470 :: (854675(Tax:4932),Gene) :: ['Fkh1p']
