Investigation of NMD factors in Schizosaccharomyces pombe

Piechocki, Kim Suzanne (2013). Investigation of NMD factors in Schizosaccharomyces pombe. University of Birmingham. M.Phil.

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Abstract

Nonsense Mediated mRNA Decay (NMD) is a translation-coupled mRNA surveillance mechanism which targets aberrant mRNAs harbouring premature termination codons (PTCs). This class of mutations would otherwise result in the translation of truncated proteins that could potentially be detrimental to the cell. Intriguingly, NMD is linked to pre-mRNA splicing: in mammalian cells PTCs induce strong NMD only in the presence of a downstream intron. In these systems, the link between pre-mRNA splicing and NMD is thought to be mediated by the Exon-Junction-Complex (EJC), which is a multiprotein complex that marks splice junctions.

In fission yeast Schizosaccharomyces pombe, pre-mRNA splicing can also enhance NMD however this mechanism does not require the EJC. To gain further insight into the mechanisms of NMD I undertook a genome-wide screen to identify and characterize additional factors that may be involved in this process in fission yeast. In particular, I hoped to identify genes required for the link between splicing and NMD. The screen consisted of crossing a GFP reporter strain subject to NMD with haploid deletion mutants of 3,308 non-essential genes in the S. pombe.

Analysis of 2790 mutants identified 18 candidates. These were further characterised by northern blot analysis. From these 18 strains, 7 mutants look like genuine NMD mutants resembling the phenotype of known NMD genes. 5 genes have either direct or indirect links with splicing factors or the exosome-associated TRAMP complex. Future work will need to elucidate the molecular mechanism of the NMD phenotype and possible involvement of these genes in splicing, NMD and the TRAMP-mediated mRNA surveillance processes

Type of Work:

Thesis (Masters by Research > M.Phil.)

Award Type:

Masters by Research > M.Phil.

Supervisor(s):