Regulatory Factors of Cyclin Functions in the Cell Cycle

根据提出的研究计划，日本九州大学的小林秀树与ICRF克莱尔霍尔实验室的蒂姆·亨特博士和英国剑桥大学的马克·卡林顿博士开展了细胞周期中细胞周期蛋白功能的合作。Hideki小林等人通过酵母双杂交筛选分离出非洲爪蟾细胞周期蛋白A结合蛋白，并鉴定出与细胞周期蛋白A N端结合并选择性抑制其降解的新蛋白THF4。蒂姆·亨特分析了爪蟾卵提取物中细胞周期的生化特性。Mark Carrington分离了THF4的鼠同源物，并鉴定了其与细胞周期蛋白A的结合结构域。总之，在双杂交筛选中使用爪蟾细胞周期蛋白A1的N-末端结构域来鉴定与细胞周期蛋白A相互作用的蛋白质。主要的相互作用物种是THF4，一种在其N-末端含有泛素样结构域的蛋白质，在酿酒酵母Dsk2和www.example.com be dph1的C-末端显示出显著的同源性。THF4持续存在 ...更多信息 在非洲爪蟾细胞中作为核磷蛋白，其磷酸化由细胞周期蛋白A依赖性激酶诱导。在体内和体外，THF4与胚胎和体细胞形式的细胞周期蛋白A（A1和A2）结合，但不与B型细胞周期蛋白结合。THF4的N-末端类似泛素的结构域（而非C-末端保守结构域）是与细胞周期蛋白A相互作用所必需的。THF4需要细胞周期蛋白A1的130 - 160位残基（不包括细胞周期蛋白A的破坏盒）才能有效结合。将THF4蛋白注入受精卵后，胚胎细胞分裂受到抑制，提示THF4可能是cyclin A的候选底物。这些结果为细胞周期蛋白的蛋白水解提供了新的思路cycle这一合作研究项目在三年（1996 - 1998）期间相当成功，我们将继续进行更多的合作研究。少

According to the proposed research plan, Hideki Kobayashi, Kyushu University in Japan, carried out the collaboration on the cyclin functions in the cell cycle, with Dr.Tim Hunt at ICRF Clare Hall Laboratories, and Dr.Mark Carrington at Cambridge University, England. Hideki Kobayashi isolated Xenopus cyclin A-binding protein by yeast 2-hybrid screen and identified the novel protein THF4 that binds to the N-terminus of cyclin A and inhibits its degradation selectively. Tim Hunt analyzed its biochemical properties on the cell cycle in Xenopus egg extracts. Mark Carrington has isolated murine homolog of THF4 and identified its binding domain to cyclin A.In summary, the N-terminal domain of Xenopus cyclin A1 was used in a 2-hybrid screen to identify proteins that interact with cyclin A.The major interacting species was THF4, a protein that contains a ubiquitin-like domain in its N-terminus shows a significant homology in the C-terminus of S.cerevisiae Dsk2 and S.porn be dph1. THF4 persists … More in Xenopus cells as a nuclear phosphoprotein and its phosphorylation is induced by cyclin A-dependent kinase. THF4 binds to both embryonic and somatic forms of cyclin A (Al and A2) in vivo and in vitro, but not to B-type cyclins. The N-terminal u1biquitin-like domain of THF4, but not the C-temimal conserved domain, is required for interaction with cyclin A.THF4 requires residues 130-160 of cyclin Al for efficient binding, which do not include the destruction box of cyclin A.The addition of bacterially-expressed THF4 protein to_frog egg extract inhibited the Ca2+-induced degradation of cyclin A, but not that of cyclin B.The injection of THF4 protein into the fertilized egg blocked the embryonic cell division.These results suggest that THF4 is a candidate substrate for cyclin A-dependent kinase and that THF4 may act as a negative regulator of cyclin A degradation in mitosis.These results would give a new insight into cyclin proteolysis in the cell cycle This collaborative research project during three years (1996-1998) was quite successful, and we will continue the collaborative research more. Less