Jin S, Yin L, Wang D S, Liu H T
Department of Biology Beijing Normal University, China.
Shi Yan Sheng Wu Xue Bao. 1995 Jun;28(2):121-9.
In order to study the role of calmodulin (CaM) in the cell cycle, RC 3 cells carring the CaM expression vectors which was constructed by joining the CaM cDNA with a plasmid of mouse mammary tumor virus (MMTV), were used in this experiment. The CaM expression vectors transcription is regulated by a dexamethasone (DXM) inducible MMTV LTR promoter. Upon addition of DXM, cells have transiently increased CaM mRNA and protein levels. Increased CaM caused a acceleration of proliferation. Flow cytometric analysis showed that progression though G1, G2 and metaphase was accelerated by increase in CaM levels, while treatment with the CaM antagonist trifluoperazine (TFP) blocked cell cycle progression at G1/S boundary and during G2/M and metaphase. The studies have shown that CaM is important in controlling progression at three points in the cell cycle: (1) The G1/S boundary to permit the initiation of DNA synthesis; (2) The G2/M boundary to permit the initiation of mitosis; (3) At the metaphase/anaphase transition of mitosis to permit chromosome segration and the completion of mitosis. This study indicates that the RC 3 cell is a useful experimental cell model for studing the effect of a transient increase of intracellular CaM levels on control of cell cycle.
为了研究钙调蛋白（CaM）在细胞周期中的作用，本实验使用了携带通过将CaM cDNA与小鼠乳腺肿瘤病毒（MMTV）质粒连接构建的CaM表达载体的RC 3细胞。CaM表达载体的转录受地塞米松（DXM）诱导的MMTV长末端重复序列（LTR）启动子调控。加入DXM后，细胞中CaM mRNA和蛋白质水平短暂升高。CaM水平升高导致细胞增殖加速。流式细胞术分析表明，CaM水平升高加速了细胞通过G1期、G2期和中期的进程，而用CaM拮抗剂三氟拉嗪（TFP）处理则在G1/S边界以及G2/M期和中期阻断细胞周期进程。研究表明，CaM在控制细胞周期的三个关键点的进程中很重要：（1）G1/S边界，以允许DNA合成的起始；（2）G2/M边界，以允许有丝分裂的起始；（3）在有丝分裂的中期/后期转换时，以允许染色体分离和有丝分裂的完成。本研究表明，RC 3细胞是研究细胞内CaM水平短暂升高对细胞周期控制的影响的有用实验细胞模型。
