Interdisciplinary Graduate Programs Symposium
2011 OSU Molecular Life Sciences
Interdisciplinary Graduate Programs Symposium
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Poster abstracts
Abstract:
Background: Cytokinesis partitions a mother cell into two daughter cells and is essential for cell proliferation and cell differentiation [1]. Septins, a group of conserved GTPases, are essential for cytokinesis in budding yeast and some animal cells. However, septin deletion mutants are viable in the fission yeast S. pombe indicating presence of a septin redundant pathway in cytokinesis [2]. A synthetic lethal screen with septin deletion mutants identified the arrestin family protein Art1 as a part of this parallel pathway [3]. Arrestins are known to regulate signalling in higher eukaryotes [4]. However, their functions in S. pombe are unknown.
Hypothesis: The art1 point mutation identified could be rescued by overexpression of the Rho-GEF Rgf3 [3], suggesting that Art1 and Rgf3 cooperate during the late stages of cytokinesis in fission yeast.
Findings: I found that 15% of art1 deletion (art1Δ) cells lysed during cell separation, the last stage of cytokinesis, indicating a plasma membrane/septal cell wall defect like in septin mutants. Art1 localized to the contractile ring during anaphase B. Deleting the C- terminus domain of Art1 mimicked art1Δ phenotype and caused loss of Art1 localization. Arrestins are known to interact with Rho-GEF proteins [5]. Rho-GEF Rgf3 is also synthetic lethal with septin and localizes to the cell division site at about the same time as Art1. I found that Art1 and Rgf3 interact in immunoprecipitation and yeast two-hybrid assays. In addition, Rgf3 and Art1 are interdependent for their localization to the contractile ring. Furthermore, I found that Art1 is phosphorylated. The findings support Art1 cooperation with Rgf3 during cytokinesis.
Significance: Art1 is the first known S. pombe arrestin being characterized. The results obtained imply a novel role for arrestins. Discovery of its function would lead to a better understanding of cytokinesis in S. pombe, with ramifications for higher eukaryotes too.
References:
1. Barr, F.A. and U. Gruneberg. Cytokinesis: placing and making the final cut. Cell, 2007. 131:847-860.
2. Martin-Cuadrado, A.B., et al. Role of septins and the exocyst complex in the function of hydrolytic enzymes responsible for fission yeast cell separation. Mol Biol Cell, 2005. 16:4867-4881.
3. Wu, J.Q., et al. Cooperation between the septins and the actomyosin ring and role of a cell-integrity pathway during cell division in fission yeast. Genetics. 186:897-915.
4. Premont, R.T. and R.R. Gainetdinov. Physiological roles of G protein-coupled receptor kinases and arrestins. Annu Rev Physiol, 2007. 69:511-534.
5. Aubry, L., D. Guetta, and G. Klein. The arrestin fold: variations on a theme. Curr Genomics, 2009. 10:133-142.
Keywords: Cytokinesis, S pombe, Art1
