CELL CYCLE GENES AND CELLULAR SENESCENCE AND AGING

培养中的正常人类细胞显示出有限的分裂潜力， 衰老 细胞分裂一定数量的世代， 未能进入后续S阶段。 现有证据表明， 衰老细胞有一个完整的途径，防止某些方面的 细胞周期调节装置的激活。 整体利益 是为了确定哪些方面的激活是缺乏的，以及是否 引入细胞周期调节基因和蛋白质， 启动子进入S期可以克服这种失活。 最近 遗传和生化证据表明，G1到S期 真核细胞周期中的过渡部分由 蛋白激酶p34 cdc 2及其相关蛋白的协调作用 调节亚单位，细胞周期蛋白。 该计划的主要重点将 分析Cdk 2和Cdc 2 Hs蛋白激酶与G1 细胞周期蛋白在衰老过程中发挥重要作用， 周期转换 Cdk 2是一种Cdc 2相关的蛋白激酶， Cdc 2激酶的不同亚家族。 目前认为Cdk 2， 与细胞周期蛋白A复合，参与DNA的控制 复制和/或G1-S过渡。 Xenopus Cdk 2的消耗 蛋白质，但不是Cdc 2蛋白质，在循环中阻断DNA复制 体外胚胎提取物。 进一步的证据表明 在细胞周期中的作用是一些CDK 2 mRNA持续存在于G 0细胞中， 当刺激G 0细胞进入细胞周期时，其mRNA水平 G1的增加先于CDC 2 Hs mRNA的增加。 本研究的具体目的是使用G1细胞周期蛋白，CDK 2和 CDC 2 Hs基因作为工具：1）探索静止期的表达状态 和衰老细胞的关键细胞周期调节因子，2） 确定去除Cdk 2和其他相关蛋白质对 细胞周期的进展，3）探索细胞周期对Cdk 2的调节 磷酸化，和4）确定是否表达的组合， 细胞周期蛋白和p34蛋白激酶可以促进进入静止期或 衰老细胞进入S期。 我们分析了衰老中G1期控制 细胞的目的是确定那些关键的调节器，其功能是 在衰老细胞中负调控。 该信息可用于 进一步阐明负调节的机制， 在衰老细胞中建立。

Normal human cells in culture show a limited division potential known as senescence. Cells divide for a defined number of generations and then fail to enter subsequent S phases. Available evidence suggests that senescent cells have intact a pathway that prevents some aspect of activation of the cell cycle regulatory apparatus. Our overall interests are to determine what aspect of activation is absent, and whether introduction of cell cycle regulatory genes and proteins that normally promote entry into S phase can overcome this inactivation. Recent genetic and biochemical evidence suggests that the G1 to S phase transition in the eukaryotic cell cycle is controlled, in part, by the coordinate action of a protein kinase(s), p34cdc2, and its associated regulatory subunits, cyclins. The principal focus of this program will be the analysis of the role that Cdk2 and Cdc2Hs protein kinases and G1 cyclins play in the process of senescence and the regulation of cell cycle transitions. Cdk2 is a Cdc2-related protein kinase that forms a distinct sub-family of Cdc2 kinases. It is currently believed that Cdk2, which is found complexed with cyclin A, is involved in the control of DNA replication and/or the G1-S transition. Depletion of the Xenopus Cdk2 protein, but not the Cdc2 protein, blocks DNA replication in cycling embryonic extracts in vitro. Further evidence suggestive of an early role in the cell cycle is that some CDK2 mRNA persists in G0 cells and, when G0 cells are stimulated to enter the cell cycle, its mRNA levels increase in G1 prior to the increase in CDC2Hs mRNAs. The specific aims of this research are to use the G1 cyclins, CDK2 and CDC2Hs genes as tools to: 1) explore the expression state of quiescent and senescent cells with respect to key cell cycle regulators, 2) determine the effects of removal of Cdk2 and other relevant proteins on the progression of the cell cycle, 3) to explore regulation of Cdk2 by phosphorylation, and 4) to determine if expression of combinations of cyclins and p34 protein kinases can promote entry of quiescent or senescent cells into S phase. Our analysis of G1 control in senescent cells is aimed at identifying those key regulators whose functions are negatively regulated in aging cells. This information can be used to further elaborate the mechanisms by which negative regulation is established in senescent cells.