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Pom1 is a polarity protein kinase in fission yeast, ''Schizosaccharomyces pombe'' (''S. pombe''), that localizes to cell ends and regulates cell division. As the cell lengthens, the level of Pom1 in the middle declines, which triggers mitosis.〔Bahler, J., and Pringle, J.R. “Pom1p, a fission yeast protein kinase that provides positional information for both polarized growth and cytokinesis.” Genes and Development 12, 1356-1370 (1998).〕 The gene ''pom1'' codes for a protein 1087 amino acids long with the protein kinase domain likely located at the carboxyl terminus.〔 Pom1 regulates a signaling pathway that includes Cdk1 and ultimately regulates mitotic entry.〔Moseley, J.B., Mayeux, A., Paoletti, A. and Nurse, P. “A spatial gradient coordinates cell size and mitotic entry in fission yeast.” Nature 459, 857-861 (2009).〕 Cells with mutant pom1 form a septa and growth zone, but show a host of abnormalities including misplaced or misoriented septa, bi-polar growth replaced with random growth at one end, or the mislocalization of the growth axis leading to abnormal branching.〔〔Bahler, J., and Nurse, P. “Fission yeast Pom1p kinase activity is cell cycle regulated and essential for cellular symmetry during growth and division.” The EMBO Journal 20, 1064-1073 (2001).〕 Pom1 plays an important role in differentiating the old and new end of an S. pombe cell. Normal cell growth begins immediately in the old end of the cell and is delayed in the new end.〔 ''pom1'' mutants show immediate growth at either end. Since Pom1 has been shown to be highly concentrated at the new end and nearly absent from the old end, it, along with other factors are part of an inhibitory signal that prevents immediate growth from the new end.〔 Overexpression of Pom1 can also lead to the formation of new growth ends.〔 Pom1 is a relatively unique protein kinase as its closest homolog in S. pombe is only 55% identical. Homologs in other organisms include Dyrk in rats, Dyrk2 and Dyrk3 in humans, Yak1p in S. cerevisiae,〔Souza, G.M., Lu, S., and Kuspa, A. “YakA, a protein kinase required for the transition from growth to development in Dictyostelium. Development 125, 2291-2302 (1998).〕 and Minibrain in Drosophila and humans.〔〔Tejedor, F., Zhu, X.R., Kaltenbach, E., Ackermann, A., Baumann, A., Canal, I., Heisenberg, M., Fischbach, K.F., and Pongs, O. “Minibrain: A new protein kinase family involved in postembryonic neurogenesis in Drosophila. Neuron 14, 287-301 (1995).〕 == Cell localization == During interphase, Pom1 resides throughout the cell including the medial cortical nodes. Pom1’s localization to the poles during cell division is regulated by Tea1 and Tea2.〔Browning, H., Hayles, J., Mata, J., Aveline, L., Nurse, P. and McIntosh, J.R. “Tea2p is a kinesin-like protein required to generate polarized growth in fission yeast.” The Journal of Cell Biology 151,15-27 (2000).〕〔Behrens, R., and Nurse, P. “Roles of fission yeast tea1p in the localization of polarity factors and in organizing the microtubular cytoskeleton.” The Journal of Cell Biology 157, 783-793 (2002).〕 In the absence of Tea1 and Tea2, Pom1 maintains its kinase activity, but does not localize to the cell ends.〔〔 Microtubules also help localize Pom1 in the cell as Pom1 delocalization has been shown to result from microtubule disassembly.〔 Structurally, both the catalytic and non-catalytic regions of Pom1 are necessary for cell end localization.〔 The Cdr2, Cdr1, Wee1, Mid1, and Blt1 proteins are also located at the medial node during interphase and are believed to be part of the signaling pathway for mitotic entry.〔〔Morrell, J.L., Nichols, C.B., and Gould, K.L. “The GIN4 family kinase, Cdr2p, acts independently of septins in fission yeast. The Journal of Cell Science 117, 5293-5302 (2004).〕 Cdr2 localization to the cell middle is regulated by the expression of Pom1 and other signals as pom1 mutants allow Cdr2 to diffuse from the medial node localization to one half of the cell.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pom1」の詳細全文を読む スポンサード リンク
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