Publication Date

2008-01-01

Availability

Open access

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry and Molecular Biology (Medicine)

Date of Defense

2008-03-30

First Committee Member

Arun Malhotra

Second Committee Member

Roland Jurecic

Third Committee Member

Murray Deutscher

Fourth Committee Member

Mary Lou King

Abstract

The spatio-temporal regulation of translation is critical to the proper development of all organisms. The presence of Translational Control Elements (TCEs) in Un-Translated Regions (UTRs) is one feature common to all regulated eukaryotic mRNAs examined to date. These TCEs serve as binding sites for sequence specific proteins or small regulatory RNAs that recruit other accessory proteins that inhibit translation. Xnos1, a localized RNA in the germ plasm of Xenopus, is negatively regulated by an unknown mechanism. We used in vivo and in vitro translation assays, competition assays, and ribosome binding assays in order to determine the location of the Xnos1 TCE and its mechanism of repression. The Xnos1 TCE is located in the open reading frame, a departure from the canonical translational regulation mechanisms. This TCE is predicted to form conserved secondary structures in the first 75 nucleotides of the open reading frame (ORF). In vitro translation assays demonstrated that the repression can be partially relieved by either denaturing the transcripts or by introducing point mutations that weaken the secondary structure. This TCE cannot be relieved by competition and therefore is likely not to require the presence of a repressor protein. The structural regulation of translation by a TCE in the open reading frame is a novel mechanism of repression for a eukaryotic mRNA.

Keywords

Translation; Xnos1; Secondary Strucutre

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