Sim Khe Guan, Cheong Jit Kong, Hsu Stephen I-Hong
Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore.
Cell Cycle. 2006 May;5(10):1111-5. doi: 10.4161/cc.5.10.2797. Epub 2006 May 15.
The G1 D-type cyclins, in conjunction with cyclin-dependent kinases Cdk4 and Cdk6, play key roles in the execution of mitogen-induced cellular proliferation. TRIP-Br1, a member of the TRIP-Br family of transcriptional regulators, has been implicated in the regulation of Cdk4/cyclin D activity. To further elucidate the functional role(s) of the TRIP-Br proteins in mitogenic signaling, we have developed the synthetic DNA enzymes E-Br1 and E-Br2 to specifically knock down the serum-inducible expression of TRIP-Br1 and TRIP-Br2, respectively, in WI-38 human fibroblasts in culture, as well as generated TRIP-Br2 null primary embryonic fibroblasts from a novel TRIP-Br2 knockout mouse model. Both strategies consistently reveal that ablation of TRIP-Br1 or TRIP-Br2 expression disrupts mitogenic signaling in a manner that suppresses serum-induced cyclin E expression, S-phase entry and cellular proliferation. We conclude that both TRIP-Br1 and TRIP-Br2 are required for proper transduction of mitogenic signals and execution of serum-inducible cell cycle progression.
G1期D型细胞周期蛋白与细胞周期蛋白依赖性激酶Cdk4和Cdk6共同作用，在有丝分裂原诱导的细胞增殖过程中发挥关键作用。TRIP-Br1是转录调节因子TRIP-Br家族的成员之一，与Cdk4/细胞周期蛋白D活性的调节有关。为了进一步阐明TRIP-Br蛋白在有丝分裂信号传导中的功能作用，我们开发了合成DNA酶E-Br1和E-Br2，以分别特异性敲低培养的WI-38人成纤维细胞中血清诱导的TRIP-Br1和TRIP-Br2的表达，并从一种新型的TRIP-Br2基因敲除小鼠模型中获得了TRIP-Br2基因缺失的原代胚胎成纤维细胞。两种策略均一致表明，TRIP-Br1或TRIP-Br2表达的缺失会以抑制血清诱导的细胞周期蛋白E表达、S期进入和细胞增殖的方式破坏有丝分裂信号传导。我们得出结论，TRIP-Br1和TRIP-Br2都是有丝分裂信号的正确转导和血清诱导的细胞周期进程执行所必需的。
