Initiation of Translation of Eukaryotic Messenger-Rna at a Unique Site Lacking an AUG Codon
Woessner, Richard Donald
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https://hdl.handle.net/2142/72350
Description
Title
Initiation of Translation of Eukaryotic Messenger-Rna at a Unique Site Lacking an AUG Codon
Author(s)
Woessner, Richard Donald
Issue Date
1988
Doctoral Committee Chair(s)
Clark, John M., Jr.
Department of Study
Biochemistry
Discipline
Biochemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Abstract
The initiation of translation of eukaryotic mRNA is believed to proceed by a "scanning mechanism" where the ribosome recognizes a 5$\sp\prime$ terminal cap structure (m$\sp7$GpppN ...) and then scans down the mRNA until reaching the first 5$\sp\prime$ terminal AUG or $\sp{\rm A}\sb{\rm G}$XXAUG$\sp{\rm A}\sb{\rm G}$. The RNA from satellite tobacco necrosis virus (STNV RNA) is unusual in that it contains no cap structure but functions as an efficient eukaryotic mRNA. This suggests that STNV RNA contains features involved in the initiation of translation of eukaryotic mRNA in addition to those of the scanning model. To investigate this theory, 40 base sequences containing variations of the translation initiation region of STNV RNA were cloned into the pSP64 plasmid. Linearization of these plasmids with appropriate restriction enzymes followed by runoff transcription yields short mRNAs which code for defined proteins. This approach allows study of the role of specific nucleotides or nucleotide combinations in the initiation of translation. Surprisingly, such short mRNAs containing CCC in place of the initiator AUG are $\sim$30% as efficient in synthesis of a defined protein during in vitro translation. Initiation of translation at a codon totally different from AUG is unique among eukaryotic mRNAs and suggests that the STNV RNA translation initiation region contains special features in addition to those of the scanning model that enhance the initiation of translation. Identification of these features will lead to a better understanding of translation initiation in eukaryotes and may provide efficient translation initiation sequences for use in construction of synthetic eukaryotic genes.
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