Deletion of Rnt1p Alters the Proportion of Open versus Closed rRNA Gene Repeats in Yeast

Abstract

In Saccharomyces cerevisiae, the double-stranded-RNA-specific RNase III (Rnt1p) is required for the processing of pre-rRNA and coprecipitates with transcriptionally active rRNA gene repeats. Here we show that Rnt1p physically interacts with RNA polymerase I (RNAPI) and its deletion decreases the transcription of the rRNA gene and increases the number of rRNA genes with an open chromatin structure. In contrast, depletion of ribosomal proteins or factors that impair RNAPI termination did not increase the number of open rRNA gene repeats, suggesting that changes in the ratio of open and closed rRNA gene chromatin is not due to a nonspecific response to ribosome depletion or impaired termination. The results demonstrate that defects in pre-rRNA processing can influence the chromatin structure of the rRNA gene arrays and reveal links among the rRNA gene chromatin, transcription, and processing.

ACKNOWLEDGMENTS

We thank R. J. Wellinger for critical reading of the manuscript and for yeast strain LLY112, T. R. Hughes for yeast strain R1158, B. Séraphin for plasmid pBS1539, and T. Ito for plasmids pGAD-RPA12 and pGAD-RPA34. We also thank M. Riva for providing antibodies against Rpa34p and Rpa49p. We are indebted to Nick J. Proudfoot for the communication of unpublished data and helpful discussion.

This work was supported by grant 216854-04 from the Natural Sciences and Engineering Research Council of Canada (NSERC). Support for the RNA group core was provided by CIHR. S.A. is a Chercheur Boursier Senior of the Fonds de la Recherche en Santé du Québec. M.T. and A.C. were supported by NSERC grant 326873-06.