"Cytokinesis is the division of a cell into two daughter cells. Cytokinesis failure results in polyploidy, which may contribute to tumorigenesis or cause cell death. The Saccharomyces cerevisiae protein Hof1, which is required for efficient cytokinesis, is phosphorylated during mitosis. The hypothesis that MEN (mitotic exit network) dependent phosphorylation regulates Hof1 degradation, triggering completion of cytokinesis was tested. Hof1 contains a PEST sequence, which is rich in proline, glutamic acid, serine, and threonine, and is believed to be involved in protein degradation. To test the hypothesis, we created two non-phosphorylatable mutants of the Hof1 PEST domain tagged with GFP. The first mutant is a 5A which has the first five serines replaced with alanine. The second mutant is a 10A which has nine serines and one threonine replaced with alanine. Using time-lapse microscopy we have shown that phosphorylation of the Hof1 PEST domain is required to remove Hof1 from the bud neck after cytokinesis. We used Myo1-GFP to determine if lack of PEST phosphorylation affects contraction, and our results show that it does. No cytokinesis defects were seen in cells lacking PEST domain phosphorylation. Our results suggest that neither removal of Hof1 from the bud neck nor degradation of Hof1 is required for completion of cytokinesis. Our data shows that the interaction of Hof1 with Grr1, a protein that is involved with degradation, is not regulated by PEST domain phosphorylation"--Abstract, page iii.
M.S. in Applied and Environmental Biology
Missouri Life Sciences Research Board
Missouri University of Science and Technology
viii, 45 pages
© 2011 Katherine Elizabeth Stockstill, All rights reserved.
Thesis - Open Access
Fungal molecular biology
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Link to Catalog Record
Stockstill, Katherine E., "Mutation of the Hof1 pest domain affects cytokinesis in budding yeast" (2011). Masters Theses. 5014.