engleski

The RSC remodeling complex as essential component of the remodeler network for chromatin remodeling at the yeast PHO5 promoter

The yeast PHO5 promoter was the first and still is one of the best characterized examples of a massive chromatin transition that is an absolute prerequisite for transcription activation. The comprehensive search for involved cofactor(s) revealed a complex network of five remodelers from all four major subfamilies in yeast. We showed recently that RSC, the only remodeling complex essential for viability in yeast, is a major component of this network. In continuation we wished to fully clarify the role of RSC, especially if it is essential for PHO5 promoter opening. We applied new strategies for more complete RSC ablation than the previous inactivation of its catalytic subunit Sth1 by the temperature sensitive degron allele sth1td. First, we combined the deletion of RSC2, encoding a subunit of a major RSC complex isoform, with inactivation of Sth1td during PHO5 induction at the nonpermissive temperature (37 °C). Second, we constructed a double mutant containing a Tet-Off-promoter driven STH1 gene and the rsc2 deletion allele and examined chromatin remodeling upon physiological induction at 30 °C. In contrast to the sth1td single mutant, both double mutants achieved no appreciable PHO5 promoter opening even after prolonged induction suggesting an essential role of RSC complex. Interestingly, chromatin remodeling at PHO8 and PHO84 promoters, coactivated with PHO5 by the same transactivator Pho4, was not significantly affected even under such strong ablation of RSC complex. Chromatin remodeling at a PHO5 promoter variant activated by the non-physiological activator Gal4 was also fully prevented in both double mutants, showing that the RSC effect is not specific for induction through PHO signaling nor for promoter activation by the native activator Pho4. We also demonstrated that RSC activity is not only essential for opening but also for the maintenance of open chromatin at the PHO5 promoter.

chromatin remodeling ; gene transcription ; yeast PHO5

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