| Popis: |
We showed recently that a network of five remodeling complexes is involved in chromatin remodeling at the PHO5 promoter and postulated that the RSC complex has a major role in promoter opening (1, 2). To distinguish if this role is even essential, a new strategy for more complete depletion of RSC activity was now applied. We combined the thermal inactivation of the degron-tagged catalytic RSC subunit Sth1, which was used in our previous study, with the viable deletion allele of the gene encoding the Rsc2 subunit of the major RSC isoform. In this double mutant, inactivation of RSC was so strong that chromatin remodeling at the PHO5 promoter was prevented. Further, RSC activity was not only required for initial promoter opening but also for the maintenance of the open chromatin state. Interestingly, in the same mutant cells chromatin remodeling at the PHO8 and PHO84 promoters, which are activated by the same activator Pho4 as the PHO5 promoter, was hardly affected. By using a temperature-sensitive allele coding for the essential RSC subunit Arp9, we demonstrated the critical importance of the Arp module for RSC activity using RSC’s essential role at the PHO5 promoter as read-out. However, this essential RSC requirement did not correspond to a mechanistically essential role, as an artificial increase of promoter recruiting and activation potential by overexpression of Pho4 resulted in substantial chromatin opening in the rsc2 sth1-td mutant, but significantly less in snf2 sth1-td mutant. Altogether, we showed here that appreciable chromatin remodeling at the PHO5 promoter cannot occur in vivo without participation of remodeling complexes and that the contribution of the RSC complex is essential under physiological conditions but can be replaced mechanistically by other remodelers under Pho4 overexpression. References: [1] Korber P, Barbaric S. Nucleic Acids Res. 2014, 42:10888-10902. [2] Musladin S, Krietenstein N, Korber P, Barbaric S. Nucleic Acids Res. 2014, 42:4270-4282. |
