Rsc4 Connects the Chromatin Remodeler RSC to RNA Polymerases

Abstract

RSC is an essential, multisubunit chromatin remodeling complex. We show here that the Rsc4 subunit of RSC interacted via its C terminus with Rpb5, a conserved subunit shared by all three nuclear RNA polymerases (Pol). Furthermore, the RSC complex coimmunoprecipitated with all three RNA polymerases. Mutations in the C terminus of Rsc4 conferred a thermosensitive phenotype and the loss of interaction with Rpb5. Certain thermosensitive rpb5 mutations were lethal in combination with an rsc4 mutation, supporting the physiological significance of the interaction. Pol II transcription of ca. 12% of the yeast genome was increased or decreased twofold or more in a rsc4 C-terminal mutant. The transcription of the Pol III-transcribed genes SNR6 and RPR1 was also reduced, in agreement with the observed localization of RSC near many class III genes. Rsc4 C-terminal mutations did not alter the stability or assembly of the RSC complex, suggesting an impact on Rsc4 function. Strikingly, a C-terminal mutation of Rsc4 did not impair RSC recruitment to the RSC-responsive genes DUT1 and SMX3 but rather changed the chromatin accessibility of DNases to their promoter regions, suggesting that the altered transcription of DUT1 and SMX3 was the consequence of altered chromatin remodeling.

Supplemental material for this article may be found at http://mcb.asm.org/.

We thank C. Boschiero for help with the experiments, O. Harismendy for help with the Northern analysis, M. Kabani for the GST and GST-Anc1 proteins, E. Favry for the homogeneous yeast Pol III preparation, and the DRIP for the monoclonal antibodies. We especially thank P. Thuriaux and A. Sentenac for reading and improving the manuscript.

V.B.-L.F. was supported by a grant from the Association pour la Recherche contre le Cancer. This study was supported by grants from HFSPO, the MENRT, and the ARC.