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首页> 外文期刊>Journal of Cellular Physiology >Expression and subcellular localization of CDK2 and cdc2 kinases and their common partner cyclin A in thyroid epithelial cells: comparison of cyclic AMP-dependent and -independent cell cycles.
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Expression and subcellular localization of CDK2 and cdc2 kinases and their common partner cyclin A in thyroid epithelial cells: comparison of cyclic AMP-dependent and -independent cell cycles.

机译：CDK2表达和亚细胞定位和cdc2细胞周期蛋白激酶和他们共同的伙伴一个在甲状腺上皮细胞:比较循环AMP-dependent和独立的细胞周期。

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摘要

Dog thyroid epithelial cells in primary culture constitute a model of positive control of DNA synthesis initiation and G0-S prereplicative phase progression by cyclic AMP as a second messenger for TSH. In tis early steps, this mitogenic control is quite distinct from cyclic AMP-independent mitogenic cascades elicited by growth factors. We demonstrate here that TSH (cyclic AMP) and EGF+serum (cyclic AMP-independent) stimulations cooperate and finally converge on proteins that control the cell cycle machinery. This convergence included a common induction of the expression of cyclin A and p34cdc2, and to a lesser extent of p33/38cdk2, which was already expressed in quiescent thyroid cells, and common changes of cdc2 and CDK2 phosphorylations as evidenced by electrophoretic mobility shifts. Kinetic differences in these processes after stimulation by TSH or EGF+serum or by these factors in combination correlated with differences in cell cycle kinetics. Moreover, an immunofluorescence analysis of these proteins using the double labeling of PCNA as a marker of each cell cycle phase shows: (1) a previously undescribed nuclear translocation of CDK2 before S phase initiation; (2) a sudden increase of cdc2 nuclear immunoreactivity at G2/mitosis transition. These data support the roles of CDK2 and cdc2 at G1/S and G2/mitosis transitions, respectively. (3) We were unable to demonstrate in individual cells a strict association between the nuclear appearance of cyclin A and G1/S transition, and an association of cyclin A and CDK2 with PCNA-stained DNA replication sites. On the other hand, the lengthening of G2 phase in the TSH/cyclic AMP-dependent thyroid cell cycle was associated with a stabilization of Tyr15 inhibitory phosphorylation of cdc2 and an especially high nuclear concentration of cyclin A and CDK2. We hypothesize that high nuclear accumulation of cyclin A and CDK2 during G2 phase could be causative in the cyclic AMP-dependent delay of mitosis onset.
机译：狗甲状腺上皮细胞在初级文化积极的控制基因的构成模型合成起始和G0-S prereplicative环腺苷酸作为第二阶段发展信使TSH。从循环促有丝分裂的控制是截然不同的AMP-independent促有丝分裂的瀑布了生长因子。(环腺苷酸)和血清EGF +(循环AMP-independent)刺激和合作终于在蛋白质控制收敛细胞周期机械。共同诱导的细胞周期蛋白的表达和p34cdc2,程度较轻p33/38cdk2,已经表达静止的甲状腺细胞,和共同的变化cdc2、CDK2磷酸化就是明证电泳迁移率变化。刺激后这些过程的差异通过血清TSH或EGF +或这些因素组合与不同的细胞循环动力学。使用双分析这些蛋白质增殖细胞核抗原的标记的标记每一个细胞周期阶段显示:(1)一个之前从未描述核CDK2在S期起始的易位;(2) cdc2核的突然增加免疫反应性在G2 /有丝分裂过渡。数据支持的角色CDK2和cdc2 G1 / S分别有丝分裂和G2 /转换。无法证明在单个细胞严格的核外观之间的联系细胞周期蛋白和G1 / S过渡,一个细胞周期蛋白和CDK2。协会PCNA-stained DNA复制网站。一方面,G2期的延长TSH /循环AMP-dependent甲状腺细胞周期Tyr15稳定抑制磷酸化cdc2和一个尤其是高核细胞周期蛋白的浓度CDK2。细胞周期蛋白的积累和CDK2在G2期可以循环AMP-dependent使役动词有丝分裂发生的延迟。

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