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Conditional defect in mRNA 3' end processing caused by a mutation in the gene for poly(A) polymerase.
1Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642.
Molecular and Cellular Biology
|July 1, 1992
Summary
Researchers identified a Saccharomyces cerevisiae mutant defective in polyadenylation, revealing PAP1
Area of Science:
- Molecular Biology
- Yeast Genetics
- RNA Processing
Background:
- Eukaryotic mRNA 3' end maturation involves cleavage and polyadenylation of precursor mRNAs.
- Understanding mRNA 3' end processing mechanisms is crucial for gene expression regulation.
Purpose of the Study:
- To investigate the mechanism and function of mRNA 3' end processing.
- To identify and characterize genes involved in polyadenylation in Saccharomyces cerevisiae.
Main Methods:
- Isolation and genetic analysis of a temperature-sensitive polyadenylation-defective mutant in Saccharomyces cerevisiae.
- Biochemical analysis of cellular extracts to pinpoint the defect in polyadenylation.
- Molecular cloning and characterization of the wild-type PAP1 gene.
- In vivo analysis of mRNA levels and structure following temperature shift.
Main Results:
- A single mutation caused both polyadenylation defects and temperature sensitivity for growth.
- The defect occurs after pre-mRNA cleavage but before polyadenylation.
- The mutated gene, PAP1, encodes a known poly(A) polymerase.
- Mutant cells produced poly(A)-deficient mRNAs at the nonpermissive temperature, yet translation persisted.
Conclusions:
- The PAP1 gene is essential for mRNA 3' end formation in Saccharomyces cerevisiae.
- The pap1-1 mutation affects a post-cleavage step in polyadenylation.
- The persistence of translation despite poly(A)-deficient mRNA suggests complex regulatory mechanisms.