Garner Andrew P, Weston Claire R, Todd Daniel E, Balmanno Kathryn, Cook Simon J
Inositide Laboratory, Signalling Programme, The Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK.
Oncogene. 2002 Nov 21;21(53):8089-104. doi: 10.1038/sj.onc.1206000.
Whilst many studies have examined the role of the MAP Kinases in regulating the G1-->S transition, much less is known about the function of these pathways in regulating other cell cycle transitions. Stimulation of the conditional mutant Delta MEKK3:ER* in asynchronous hamster (CCl39) and rat (Rat-1) fibroblasts resulted in the strong activation of endogenous JNK and p38 but only a weak activation of ERK. Activation of Delta MEKK3:ER* inhibited cell proliferation through a combination of an initial G1 and G2 cell cycle arrest, followed by a delayed onset of apoptosis. When cells were synchronized in S phase with aphidicolin and then released, activation of Delta MEKK3:ER* resulted in the up-regulation of p21(CIP1) and a pronounced inhibition of cyclin A/CDK2 and cyclin B1/CDK1 kinase activity. Analysis of mitotic figures indicated that cells failed to enter mitosis, arresting late in G2. Delta MEKK3:ER*-mediated CDK inhibition and G2 arrest did not absolutely require p21(CIP1), since both events were observed in Rat-1 cells in which p21(CIP1) is transcriptionally silenced due to promoter methylation. Rather, CDK inhibition was associated with a down-regulation of cyclin A and B1 expression. Finally, application of the p38 inhibitor SB203580 partially restored cyclin B associated kinase activity and allowed cells to proceed through mitosis into the next G1 phase, suggesting that activation of the p38 alpha/beta 2 pathway can promote a G2 cell cycle arrest.
虽然许多研究已经探讨了丝裂原活化蛋白激酶（MAP激酶）在调节G1期向S期转变中的作用，但对于这些信号通路在调节其他细胞周期转变中的功能却知之甚少。在异步培养的仓鼠（CCl39）和大鼠（Rat-1）成纤维细胞中刺激条件性突变体Delta MEKK3:ER*，可导致内源性JNK和p38的强烈激活，但ERK的激活较弱。Delta MEKK3:ER的激活通过初始的G1期和G2期细胞周期停滞，随后延迟出现细胞凋亡，从而抑制细胞增殖。当用阿非迪霉素将细胞同步化于S期，然后释放时，Delta MEKK3:ER的激活导致p21（CIP1）上调，并显著抑制细胞周期蛋白A/CDK2和细胞周期蛋白B1/CDK1激酶活性。有丝分裂图像分析表明，细胞未能进入有丝分裂，在G2期晚期停滞。Delta MEKK3:ER*介导的CDK抑制和G2期停滞并不绝对需要p21（CIP1），因为在因启动子甲基化而使p21（CIP1）转录沉默的Rat-1细胞中也观察到了这两种情况。相反，CDK抑制与细胞周期蛋白A和B1表达的下调有关。最后，应用p38抑制剂SB203580部分恢复了与细胞周期蛋白B相关的激酶活性，并使细胞能够通过有丝分裂进入下一个G1期，这表明p38α/β2信号通路的激活可促进G2期细胞周期停滞。
