The role of anillin and ESCRT proteins in the control of cytokinesis in eukaryotes

Yaduma, Wandiahyel Gaiuson (2023) The role of anillin and ESCRT proteins in the control of cytokinesis in eukaryotes. PhD thesis, University of Glasgow.

Abstract

Cytokinesis is the final step of the cell division cycle, and the major events of the process are conserved from fungi to animal cells when cellular constituents are separated to produce two daughter cells. Cytokinesis by the fission yeast Schizosaccharomyces pombe is compromised by the loss of anillin/Mid1p and they assemble slowly into an abnormal contractile ring. Phosphorylation by aurora and polo kinase during different cell cycle steps regulates several aspects of Mid1p function. In this thesis, we focussed on understanding the genetic interactions between the mid1 and vps4 genes, the physical interactions between Mid1p and Vps4p proteins, and the mechanisms by which they work together to regulate one another during cytokinesis.

In this thesis, we identified genetic interactions between mid1 phospho-mutants plo1-ts35, ark1-ts11, and vps4∆ genes using tetrad analysis. Synthetic viabilityand morphological studies identified potentially important Mid1p amino acid residues that are required for successful cytokinesis. We observed defective growth and morphology in cells with mutations in Mid1p at serine positions 332, 523, and 531. This analysis suggested a strong genetic interaction between mid1 and vps4 genes. Furthermore, Mid1p is phosphorylated by aurora ark1 and polo plo1 kinases, genetic interactions between mid1, ark1, and plo1 kinase genes is essential for cell viability, and it is also required for the correct cellular localization of Mid1p protein. Such analysis revealed serine residues S332, S523, and S531 to be required for the Mid1p function and its interaction with vps4, ark1, and plo1 genes.

Pull-down assay was used to determine the physical interaction between the Nterminal domain, middle and C-terminal domains of Mid1p with Vps4p. We observed a positive physical interaction between the C-terminal domain and Vps4p, suggesting physical interaction between C-terminal and Vps4p. However, a negative physical interaction between N-terminal and Middle with Vps4p was observed. Bioimage analysis showed septation defects and mislocalization at serine positions S332, 523, and 531 of mid1 phospho-mutant indicating the importance of phosphorylation of Mid1p in cortical anchorage and nuclear localization during cell division. The mislocalization patterns observed present evidence that Mid1p is implicated in the recruitment of nodes and endosomal vesicle elements to drive cytokinesis processes. Combined, these data suggest a genetic and biochemical interaction between Mid1p and Vps4p is important for cytokinesis and further implied that phosphorylation of Mid1p by aurora and polo kinases is significant for this processes.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by the management of ADSCOEH, Tertiary Education Trust Fund TETFUND, and Nigerian Government for the study fellowship and funding.
• Subjects: Q Science > QR Microbiology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Supervisor's Name: McInerny, Dr. Chris and Gould, Professor Gwyn
• Date of Award: 2023
• Depositing User: Theses Team
• Unique ID: glathesis:2023-83822
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Sep 2023 09:25
• Last Modified: 25 Sep 2023 09:43
• Thesis DOI: 10.5525/gla.thesis.83822
• URI: https://theses.gla.ac.uk/id/eprint/83822

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