engleski

The RSC chromatin remodelling complex is involved in PHO5 promoter opening

The massive transition of promoter chromatin structure upon PHO5 induction was clearly demonstrated to be a prerequisite for promoter activation. A redundancy of chromatin cofactors is involved in this transition, and no single essential chromatin cofactor has been identified yet. Nonetheless, the RSC complex is one of the most abundant chromatin-remodelling complexes in yeast, can disassemble nucleosomes in vitro, and was suggested as a prime candidate for a crucial or even essential role in PHO5 promoter opening. As RSC is essential for viabilityl, we used a temperature sensitive sth1td (ATPase subunit of RSC) mutant and found a prominent role for RSC in chromatin remodelling and activation of the PHO5 promoter. Remodelling at the PHO5 promoter under physiological induction conditions in phosphate-free medium was significantly affected. The effect was even more pronounced under weaker induction conditions that induce PHO5 in otherwise repressive phosphate-rich medium. Under such conditions the stringency of cofactor requirement is generally higher. Indeed, no significant opening of PHO5 promoter chromatin was detected upon RSC inactivation. Simultaneous inactivation of the SWI/SNF and RSC complexes completely prevented remodelling at the PHO5 promoter even under almost full induction conditions demonstrating functional interplay of the two complexes. Assessing the effects of RSC inactivation at the PHO8 and PHO84 promoters, which are coactivated with PHO5, showed a differential involvement of the RSC complex in chromatin structure regulation at these three PHO promoters.

RSC cmplex; chromatin remodelling; yeast PHO promoters

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