Affiliation:
1. Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
Abstract
ABSTRACT
RNase mitochondrial RNA processing (RNase MRP) mutants have been shown to have an exit-from-mitosis defect that is caused by an increase in
CLB2
mRNA levels, leading to increased Clb2p (B-cyclin) levels and a resulting late anaphase delay. Here we describe the molecular defect behind this delay.
CLB2
mRNA normally disappears rapidly as cells complete mitosis, but the level remains high in RNase MRP mutants. This is in direct contrast to other exit-from-mitosis mutants and is the result of an increase in
CLB2
mRNA stability. We found that highly purified RNase MRP cleaved the 5′ untranslated region (UTR) of the
CLB2
mRNA in several places in an in vitro assay. In vivo, we identified RNase MRP-dependent cleavage products on the
CLB2
mRNA that closely matched in vitro products. Disposal of these products was dependent on the 5′→3′ exoribonuclease Xrn1 and not the exosome. Our results demonstrate that the endoribonuclease RNase MRP specifically cleaves the
CLB2
mRNA in its 5′-UTR to allow rapid 5′ to 3′ degradation by the Xrn1 nuclease. Degradation of the
CLB2
mRNA by the RNase MRP endonuclease provides a novel way to regulate the cell cycle that complements the protein degradation machinery. In addition, these results denote a new mechanism of mRNA degradation not seen before in the yeast
Saccharomyces cerevisiae.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
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5. Mutagenesis of
SNM1
, Which Encodes a Protein Component of the Yeast RNase MRP, Reveals a Role for This Ribonucleoprotein Endoribonuclease in Plasmid Segregation
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