Persistent Link:
http://hdl.handle.net/10150/289856
Title:
Deadenylation and mRNA decay in Saccharomyces cerevisiae
Author:
Tucker, Morgan Dean
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The process of mRNA turnover is a critical component of the regulation of gene expression. In the past few years, a discrete set of pathways for the degradation of polyadenylated mRNAs, in eukaryotic cells have been described. The major pathway of mRNA degradation in yeast occurs by deadenylation of the mRNA, which primarily leads to a decapping reaction, thereby exposing the mRNA to rapid 5' to 3' exonucleolytic degradation. A critical step in the primary pathway is decapping, since it effectively terminates the mRNA's existence and is the site of numerous control inputs. I discuss the properties of the decapping enzyme and how its activity is regulated to give rise to differential mRNA turnover. The major pathways of mRNA turnover in eukaryotic cells are initiated by shortening of the poly(A) tail. In this work, I demonstrate by several criteria that CCR4 and CAF1 encode critical components of the major cytoplasmic deadenylase in yeast. First, both Ccr4p and Caf1p are required for normal mRNA deadenylation in vivo. Second, both proteins localize to the cytoplasm. Third, Caf1p co-purifies with poly(A) specific exonuclease activity, and this activity is dependent on the presence of Ccr4p. Interestingly, because Ccr4p and Caf1p have been shown previously to interact with transcription factors, these results suggest an unexpected link between mRNA synthesis and turnover. Both the Ccr4 and Caf1 proteins have significant homology to known exonucleases, in this work I demonstrate by several criteria that CCR4 encodes the catalytic subunit of the deadenylase. First, over-expression of Ccr4p rescues the deadenylation defects of a caf1Δ strain, indicating that Caf1p is not essential for deadenylation. Second, purification of Ccr4p co-purifies with poly(A) specific exonuclease activity, and this activity is not dependent on the presence of Caf1p. Third, point mutants in predicted catalytic residues of the Ccr4p exonuclease domain result in deadenylation defects in vivo and in vitro. The strong conservation of Ccr4p and Caf1p in other eukaryotes suggests that they will function in the process of deadenylation in other organisms.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Molecular.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Molecular and Cellular Biology
Degree Grantor:
University of Arizona
Advisor:
Parker, Roy

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleDeadenylation and mRNA decay in Saccharomyces cerevisiaeen_US
dc.creatorTucker, Morgan Deanen_US
dc.contributor.authorTucker, Morgan Deanen_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe process of mRNA turnover is a critical component of the regulation of gene expression. In the past few years, a discrete set of pathways for the degradation of polyadenylated mRNAs, in eukaryotic cells have been described. The major pathway of mRNA degradation in yeast occurs by deadenylation of the mRNA, which primarily leads to a decapping reaction, thereby exposing the mRNA to rapid 5' to 3' exonucleolytic degradation. A critical step in the primary pathway is decapping, since it effectively terminates the mRNA's existence and is the site of numerous control inputs. I discuss the properties of the decapping enzyme and how its activity is regulated to give rise to differential mRNA turnover. The major pathways of mRNA turnover in eukaryotic cells are initiated by shortening of the poly(A) tail. In this work, I demonstrate by several criteria that CCR4 and CAF1 encode critical components of the major cytoplasmic deadenylase in yeast. First, both Ccr4p and Caf1p are required for normal mRNA deadenylation in vivo. Second, both proteins localize to the cytoplasm. Third, Caf1p co-purifies with poly(A) specific exonuclease activity, and this activity is dependent on the presence of Ccr4p. Interestingly, because Ccr4p and Caf1p have been shown previously to interact with transcription factors, these results suggest an unexpected link between mRNA synthesis and turnover. Both the Ccr4 and Caf1 proteins have significant homology to known exonucleases, in this work I demonstrate by several criteria that CCR4 encodes the catalytic subunit of the deadenylase. First, over-expression of Ccr4p rescues the deadenylation defects of a caf1Δ strain, indicating that Caf1p is not essential for deadenylation. Second, purification of Ccr4p co-purifies with poly(A) specific exonuclease activity, and this activity is not dependent on the presence of Caf1p. Third, point mutants in predicted catalytic residues of the Ccr4p exonuclease domain result in deadenylation defects in vivo and in vitro. The strong conservation of Ccr4p and Caf1p in other eukaryotes suggests that they will function in the process of deadenylation in other organisms.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Molecular.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineMolecular and Cellular Biologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorParker, Royen_US
dc.identifier.proquest3010227en_US
dc.identifier.bibrecord.b41612863en_US
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