Date Approved
1-2016
Document Type
Dissertation
Degree Name
PhD in Cell and Molecular Biology
Department
Molecular Biology
College
Graduate School of Biomedical Sciences
Funder
National Institutes of Health (CA-ROI099003, GM-RO1086788); Founders of the University of Medicine and Dentistry of New Jersey Scholar Society; UMDNJ Research Scholars Foundation
First Advisor
Randy Strich, PhD
Committee Member 1
Michael Henry, PhD
Committee Member 2
Katrina Cooper, PhD
Committee Member 3
David Wiest, PhD
Committee Member 4
Dimitri Pestov, PhD
Subject(s)
Saccharomyces cerevisiae; Eukaryotic Initiation Factors; Genetic Translation; mRNA Translation; Protein Biosynthesis; Meiosis; Developmental Gene Expression Regulation
Disciplines
Cell and Developmental Biology | Cell Biology | Developmental Biology | Molecular Biology | Molecular Genetics
Abstract
The execution of meiosis and spore formation in S. cerevisiae requires a transient transcription program that is initiated by Ime I-dependent destruction of the repressor Ume6. IMEJ transcription is tightly contro1led by both cell type and nutritional cues but how its translation is regulated has been unknown. This study demonstrates that Rpl22A and Rpl22B, eukaryotic-specific ribosomal protein paralogs of the 60S large subunit, are required for efficient Ime I translation. While IME1 mRNA is induced normally in the absence of both para logs following transfer to sporulation medium, Ume6 remains stabilized, downstream early meiotic gene remain repressed, and development is arrested prior to Anaphase I. We find that Rpl22 and IME1 's unusually long 5'UTR play opposing roles in the translation of Ime1. Although deleting the 5 'UTR restores Ime I levels and early meiotic gene transcription in rpl22 mutants, only a modest increase in spore formation was observed suggesting that Rpl22 has additional execution points later in meiosis. Rpl22 is also required for invasive and pseudohyphal growth, implying a more general role in regulating cell fate switches responding to low nitrogen levels. Deleting both RPL22 paralogs resulted in aberrant polysome profiles, including the reduction of free 60S subunits and the appearance of halfmers, indicative ofmRNAs bound by an unpaired 40S subunit, under conditions of high translational output. Furthermore, limiting nitrogen conditions alleviate halfmer accumulation in rpl22Δ polysomes, and in poor growth conditions, mimic wild type polysomes. Because rpl22Δ cells grow slower and incorporate amino acids less efficiently than wild-type cells, but appear to have higher levels of polysome associated mRNA relative to unbound mRNA, Rpl22 may play a role in modulating the processivity of the ribosome. These findings suggest that Rpl22A and Rpl22B are conserved components of the ribosome that selectively translate developmentally regulated mRNAs.
Recommended Citation
Kim, Stephen, "Functional Analysis of Rpl22: Coordinating Differentiation Signals and Developmental Gene Translation to Promote Cell Fate Decisions" (2016). Graduate School of Biomedical Sciences Theses and Dissertations. 60.
https://rdw.rowan.edu/gsbs_etd/60
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