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Tang, Z., Mandel, L., Yean, S.-L., Lin*, C.X., Chen*, T., Yanagida, M., and Lin, R.-J.. 2003. The Kic1 Kinase of Schizosaccharomyces pombe Is a CLK/STY Orthologue That Regulates Cell-Cell Separation. Experimental Cell Research 283: 101-115. Full Article

The CLK/STY kinases are a family of dual-specificity protein kinases implicated in the regulation of cellular growth and differentiation. Some of the kinases in the family are shown to phosphorylate serine–arginine-rich splicing factors and to regulate pre-mRNA splicing. However, the actual cellular mechanism that regulates cell growth, differentiation, and development by CLK/STY remains unclear. Here we show that a functionally conserved CLK/STY kinase exists in Schizosaccharomyces pombe, and this orthologue, called Kic1, regulates the cell surface and septum formation as well as a late step in cytokinesis. The Kic1 protein is modified in vivo, likely by phosphorylation, suggesting that it can be involved in a control cascade. In addition, kic1+ together with dsk1+, which encodes a related SR-specific protein kinase, constitutes a critical in vivo function for cell growth. The results provide the first in vivo evidence for the functional conservation of the CLK/STY family through evolution from fission yeast to mammals. Furthermore, since cell division and cell–cell interaction are fundamental for the differentiation and development of an organism, the novel cellular role of kic1+ revealed from this study offers a clue to the understanding of its counterparts in higher eukaryotes.

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