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Title: Mediators of pre-mRNA splicing regulate sister chromatid cohesion in mammalian cells
Author: Sundaramoorthy, S.
ISNI:       0000 0004 5363 1607
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2014
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The ‘endless forms most beautiful’ that populate our planet rely on the process of cell division to ensure equal segregation of the cellular content including the DNA to the two daughter cells. The accurate segregation of chromosomes in eukaryotes relies on connection between replicated sister chromatids, a phenomenon known as sister chromatid cohesion. Sister chromatid cohesion is mediated by a conserved ring-like protein complex known as cohesin. Defects in this process can promote aneuploidy and contribute to meiotic segregation errors with adverse consequences for developing embryos. Despite numerous advances into understanding cell division at the molecular level, we still lack a comprehensive list of the participating proteins and complexes. The aim of this thesis was to use available functional genomic and proteomic data to identify novel regulators of mitosis in human cells. Using an RNAi approach, we identified a set of factors involved in pre-mRNA splicing whose depletion prevents successful cell division. Loss of these splicing factors leads to a failure in chromosome alignment and to a protracted mitotic arrest that is dependent on the spindle assembly checkpoint. This mitotic phenotype was accompanied by a dramatic loss of sister chromatid cohesion that we could show happens as soon as DNA replication. While depletion of pre-mRNA splicing mediators had no effect on cohesin loading onto chromatin, it prevented the stable association of cohesin with chromatin. Immunoblotting revealed that the depletion of splicing factors caused a 5-fold reduction in the protein levels of Sororin, a protein required for stable association of cohesin with chromatin in post-replicative cells. Further analysis suggests erroneous splicing of Sororin pre-mRNA upon depletion of splicing factors. Importantly, the sister chromatid cohesion loss caused by depletion of splicing factors could be suppressed by a Sororin transgene that lacks introns. Our results suggest that that pre-mRNA splicing of Sororin is a rate-limiting step in the maintenance of sister chromatid cohesion in human cells. Our work reveals that a primary cellular pathology of compromised pre-mRNA splicing is a mitotic arrest accompanied by split sister chromatids. Our work linking splicing and sister chromatid cohesion has implications for the pathology of Chronic Lymphocytic Leukemia (CLL). One of the splicing factors that we implicate in sister chromatid cohesion is SF3B1, whose gene is one of the most frequently mutated genetic drivers found in CLL patients.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available