engleski

Multiple partially redundant pathways are involved in chromatin structure remodeling at the yeast PHO84 promoter

The yeast PHO5 and PHO8 promoters were extensively studied by us and others as a model system for elucidation of promoter regulation by chromatin structure remodeling. We have previously shown that requirements for chromatin modifying and remodeling cofactors at these two promoters were rather different even though they are both activated by the same specific activator. In order to get better understanding of cofactor requirement mechanisms we included a third, the strongest PHO promoter, PHO84 in our study. Upon induction under phosphate starvation conditions, chromatin remodeling at the PHO84 promoter leads to the eviction of histones resulting in an extensive nucleosome-free region. The eviction of the two nucleosomes is strongly dependent on chromatin remodeling complexes SWI/SNF and Ino80 and histone acetyltransferase Gcn5. Interestingly, for the first time we found that the two nucleosomes at the same promoter showed markedly different degree of cofactors requirement ; remodeling of one is strictly dependent on SWI/SNF, while the other is completely remodeled in the absence of both the SWI/SNF and Ino80 complexes. The essential, most abundant chromatin remodeling complex, RSC, affects nucleosome remodeling at PHO84 and PHO5 promoters but is not critically required. The histone chaperone Asf1 also has stimulating role in chromatin remodeling at both PHO5 and PHO84 promoters, at least in part through its essential action on histone H3K56 acetyltransferase Rtt109.

chromatin remodeling; transcriptional regulation; yeast PHO genes

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