Investigating the link between translation and nonsense-mediated mRNA decay

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Petrić Howe, Marija (2019). Investigating the link between translation and nonsense-mediated mRNA decay. University of Birmingham. Ph.D.

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Abstract

Nonsense mediated mRNA decay (NMD) is regarded as an active cellular surveillance mechanism that eliminates mRNAs that contain a premature translation termination codon (PTC). In this study, I present an alternative hypothesis, formulated as the ribosome release model, which proposes that NMD may occur as a passive consequence of general roles that NMD factors play in ribosome release upon translation termination. I tested this directly, by looking at whether NMD factors affect NMD reporter mRNA association with the ribosomes. I also analysed the role of NMD factors in general translation and their association with translating mRNAs. My data indicates that NMD factors do bind mRNAs undergoing translation, regulating translation of many transcripts, and indeed possibly triggering ribosome release from mRNAs upon termination. Additionally, I found that UPF1 associates with ribosome-free RNA granules in the cell, into which in stress conditions, when global translation is impaired, it almost entirely re-distributes, possibly sequestering translationally repressed mRNAs from the translational pool. Finally, whilst investigating the role of NMD factors in translation by means of a puromycylation assay, I made unexpected observations that indicate that many complete proteins can be released from the ribosome with a tRNA still attached to the last C-terminal amino acid.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):