Knight A S, Notaridou M, Watson R J
Department of Virology, Faculty of Medicine, Imperial College London, London, UK.
Oncogene. 2009 Apr 16;28(15):1737-47. doi: 10.1038/onc.2009.22. Epub 2009 Mar 2.
It has recently been discovered that cell-cycle gene transcription is regulated by a core complex named LINC that switches from a transcriptionally repressive complex in G(0)-G(1) with the p130 or p107 pocket proteins and E2F4 to a transcriptionally active complex in S-G(2) containing B-Myb. We have studied the function of LINC in F9 embryonal carcinoma cells, which are distinguished by a rapid cell cycle resulting from an extremely short G(1) phase. We show that suppressing expression of the LINC component, Lin-9, in F9 cells causes arrest in mitosis, and we have used this system to screen for transcriptional targets. In these cells, B-Myb was found in complexes with Lin-9 and several other LINC constituents, however, the pocket proteins did not associate with LINC unless F9 cells were differentiated. Lin-9 and B-Myb were both required for transcription of G(2)/M genes such as Cyclin B1 and Survivin. Moreover, B-Myb was demonstrated to recruit Lin-9 to the Survivin promoter through multiple Myb-binding sites. The demonstration that a B-Myb/LINC complex is vital for progression through mitosis in cells lacking a G(1)/S checkpoint has implications for both undifferentiated embryonal cells and for cancers in which pocket protein function is compromised.
最近发现，细胞周期基因转录受一种名为LINC的核心复合物调控，该复合物在G(0)-G(1)期与p130或p107口袋蛋白及E2F4形成转录抑制复合物，而在S-G(2)期转变为含B-Myb的转录激活复合物。我们研究了LINC在F9胚胎癌细胞中的功能，F9胚胎癌细胞的特点是细胞周期快速，G1期极短。我们发现，抑制F9细胞中LINC组分Lin-9的表达会导致有丝分裂停滞，我们利用该系统筛选转录靶点。在这些细胞中，发现B-Myb与Lin-9及其他几种LINC成分形成复合物，然而，除非F9细胞分化，口袋蛋白不会与LINC结合。Lin-9和B-Myb都是G(2)/M期基因如细胞周期蛋白B1和生存素转录所必需的。此外，已证明B-Myb通过多个Myb结合位点将Lin-9招募至生存素启动子。在缺乏G(1)/S检验点的细胞中，B-Myb/LINC复合物对有丝分裂进程至关重要，这一发现对未分化胚胎细胞及口袋蛋白功能受损的癌症均有意义。
