Characterisation and function of nuclear RNA at mitosis in mammalian cells

El-Messeiry, Sarah Mamduh Ibrahim (2019) Characterisation and function of nuclear RNA at mitosis in mammalian cells. PhD thesis, University of Glasgow.

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The nuclear membrane encloses DNA, nuclear RNAs and proteins separating them from the surrounding cytoplasm but breaks down at the onset of mitosis allowing spindle attachment to the highly condensed mitotic chromosomes. Interphase nuclei contain a tremendous amount of RNA, and the prevailing view is that it mostly diffuses to the cytoplasm at mitosis and is inactive while there. However, using FISH and de novo RNA labelling, I found significant populations of formerly nuclear RNA to be immediately encircling and also embedded between mammalian mitotic chromosomes. These patterns were distinct from the RNA component of the perichromosomal layer (i.e. pre-rRNA) and conserved between different cell lines, and so reveal a previously unrecognised subcellular zone. The consistent patterns and large amounts of RNA involved suggested they would have essential functions at mitosis. In support of that idea, I found that globally suppressing de novo RNA transcription, but not protein synthesis, caused major mitotic aberration including failure of NMBD, loss of chromatid definition and failure to progress through mitosis. To analyse this further, I developed a novel chromosome decondensation assay based on isolated mitotic prometaphase clusters in which simple changes in Mg2+ concentration could induce dramatic and reversible decondensation. Remarkably, and contrary to all current models of mitotic chromosome condensation, I showed that RNA embedded in the cluster was the primary determinant of the degree of chromosome decondensation. These novel findings introduce RNA as a key player in mitotic chromosomal condensation, chromosome segregation and nuclear membrane break down. Also, opening up a new frontier in understanding mitotic division.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
Supervisor's Name: Hamilton, Dr. Andrew
Date of Award: 2019
Embargo Date: 28 June 2022
Depositing User: Mrs Marie Cairney
Unique ID: glathesis:2019-74272
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Jun 2019 12:40
Last Modified: 16 Feb 2020 16:18
Thesis DOI: 10.5525/gla.thesis.74272
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