Art1-Arrestin in cytokinesis
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Date
2014-02
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Abstract
Background: Cytokinesis partitions a mother cell into two daughter cells and is essential for cell proliferation and cell differentiation. Septins, a family 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 the presence of a parallel pathway for maintenance of cell integrity during cytokinesis. A synthetic lethal screen with septin deficient strain identified the arrestin Art1 as a component of this parallel pathway. Arrestins are known to regulate cellular signaling in higher eukaryotes. However, their functions in S. pombe are unknown.
Findings: I found that art1∆ (deletion) cells lysed during cell-cell separation after mitosis. Electron microscopy showed that they had a septal-wall defect that mimicked Rho GEF rgf3 mutants. Both Rho1 and Rgf3 are essential in S. pombe and have homologs in mammalian cells . Art1 and Rgf3 both accumulate at the division site during cytokinesis. IP and yeast 2 hybrid assays show that Art1 binds to Rgf3 at a region adjacent to its catalytically active GEF domain. Protein quantification revealed that loss of Art1 caused a decrease in cellular Rgf3 levels and adversely affected its contractile-ring localization. Conversely, Art1 overexpression led to an increase in cellular and contractile ring levels of Rgf3. Upon mislocalizing Art1 in the cell, Rgf3 was found to mislocalize to Art1’s location. Together, these data suggest that Art1 is involved in Rgf3 stability and its recruitment to the contractile ring. To determine the role of Art1 in Rgf3 function, we compared GTP-Rho1 localization and levels using a Rho1 biosensor and found that art1∆ cells had lower levels of active GTP-Rho1 at the division site during septum formation.
Conclusion and significance: The findings suggest that the arrestin Art1 is involved in cytokinesis by regulating Rgf3 protein stability and recruiting it to the division site. Thus art1 loss leads to lower GTP-Rho1 levels at the division site during septum formation. Art1 is the first known S. pombe arrestin characterized to have a role in cytokinesis. The results obtained imply a novel, previously unknown role for arrestins.
Description
Biological Sciences: 2nd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
Keywords
Cytokinesis, Arrestins, Rho GEF, Art1