Messenger RNA translation in Saccharomyces cerevisiae

Bettany, Andrew J.E. (1988) Messenger RNA translation in Saccharomyces cerevisiae. PhD thesis, University of Glasgow.

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The aims of this study were to investigate the effects of mRNA abundance, codon bias, and secondary structure formation upon the translation of the PYK mRNA in yeast. A method has been devised to analyse translation in vivo in the yeast S. cerevisiae. The method involves fractionation of yeast polysomes on sucrose density gradients, followed by analysis of the distribution of specific mRNAs across these polysome gradients. Experiments showed that the PYK gene of S. cerevisiae appears to be subject to dosage compensation at the translational level; the PYK mRNA carries significantly fewer ribosomes when it is present at elevated levels within the yeast cell. Experiments were also devised to analyse the effects of codon bias on the translation of the PYK mRNA. The insertion of 13 non-preferred codons into the N-terminus of the coding region of the PYK gene appeared to have no effect on the translation of this mRNA. However, the ribosome loading of a beta-galactosidase coding sequence (codon bias index = -0.05%) was shown to decrease on increasing the abundance of a beta-galactosidase/PYK fusion mRNA. This appears to be due to the detrimental effects of poor codon bias, since the translation of an mRNA with poor codon bias (TRP2) was also affected. Therefore, poor codon bias seems to have a significant influence upon the translation of an mRNA only under "extreme circumstances" (for example, when abnormally high levels of an mRNA with extremely poor codon bias are present). Increasing the secondary structure formation at the 5'-end of the PYK mRNA was also shown to decrease its ribosome loading in vivo. This is thought to be due to inhibition of translational initiation on this mRNA.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Biochemistry
Date of Award: 1988
Depositing User: Enlighten Team
Unique ID: glathesis:1988-76703
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 02 Dec 2019 10:21
Last Modified: 02 Dec 2019 10:21

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