Identification and Characterization of Suppressors for rng15 Deletion in Fission Yeast Cytokinesis

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The Ohio State University

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While much is known about cytokinesis, the final stage of cell-division cycle, our knowledge on roles of vesicle trafficking during cytokinesis is limited. To further our understanding of exocytosis during cytokinesis, we have investigated the function of Rng15 using fission yeast - a popular model organism for studying cytokinesis. Little is known about Rng15. However, our preliminary studies and its homology with Mso1 from budding yeast, suggest that it participates in exocytosis. Rng15 also shares homology to Mint1, a mammalian adaptor protein involved in exocytosis. Cells with the rng15 gene deleted (rng15∆) cannot grow at 36°C due to defective cytokinesis. They also accumulate secretory vesicles at the division site. To further investigate how Rng15 functions in cytokinesis, we screened for high-copy suppressors of rng15∆ at 36°C by transforming rng15∆ cells with plasmid DNA from a fission yeast genomic DNA library. We reasoned that if the proteins being produced from the plasmids rescue the growth of rng15∆ cells at 36°C, these proteins are involved in similar pathways as Rng15. So far we have isolated Rng15 and Gmh5 from the screen. Gmh5 is a membrane protein of the Golgi mannosyltransferase complex, which is predicted to be involved in elongation of the polysaccharide mannan backbone and cell wall biogenesis. We will study Gmh5 functions by testing its localization, deletion phenotype, and genetic interactions with rng15∆ and other mutations in cytokinesis. In addition, we plan to identify more suppressors with additional screens. Through this investigation, we will have a better understanding of the role of exocytosis in the delivery of materials during fission yeast cytokinesis. Furthermore, we hope to provide others in the field with potential insights into how the Mso1/Rng15 family proteins work in cytokinesis in other systems, including mammals.



cytokinesis, exocytosis, pombe, yeast