Degradation of Normal mRNA in the Nucleus of Saccharomyces cerevisiae

Abstract

A nuclear mRNA degradation (DRN) system was identified from analysis of mRNA turnover rates in nup116-Δ strains of Saccharomyces cerevisiae lacking the ability to export all RNAs, including poly(A) mRNAs, at the restrictive temperature. Northern blotting, in situ hybridization, and blocking transcription with thiolutin in nup116-Δ strains revealed a rapid degradation of mRNAs in the nucleus that was suppressed by the rrp6-Δ, rai1-Δ, and cbc1-Δ deletions, but not by the upf1-Δ deletion, suggesting that DRN requires Rrp6p, a 3′-to-5′ nuclear exonuclease, the Rat1p, a 5′-to-3′ nuclear exonuclease, and Cbc1p, a component of CBC, the nuclear cap binding complex, which may direct the mRNAs to the site of degradation. We propose that certain normal mRNAs retained in the nucleus are degraded by the DRN system, similar to degradation of transcripts with 3′ end formation defects in certain mutants.

ACKNOWLEDGMENTS

We thank Patricia Hinkle and John Puskas (Department of Pharmacology and Physiology, University of Rochester) for assistance in the use of the fluorescence microscope, Letian Kuai (Department of Biochemistry, University of Rochester) for assistance with processing of the fluorescence image, and Jay Greenberg (Department of Biochemistry, University of Rochester) for useful discussions. The Cy3-labeled oligo(dT) probe was kindly supplied by Pascal Chartrand (Department of Biochemistry, University of Montreal).

This work was supported by National Institutes of Health grants RO1 GM12702 (to F.S.) and RO1 GM59898 (to J.S.B.).