Spyer Moira, Allday Martin J
Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London, UK.
Cell Cycle. 2006 Mar;5(5):530-7. doi: 10.4161/cc.5.5.2524. Epub 2006 Mar 1.
CtBP is a corepressor of transcription that acts by inhibiting coactivators and recruiting to promoter control elements (via interactions with DNA-binding transcription factors) a complex of proteins that modify histones, repress transcription and silence gene expression. There are two highly homologous genes, CtBP1 and CtBP2 that encode CtBP. In addition, a CtBP1-related protein has been described that has 11 fewer amino acids at its N-terminus than CtBP1. This variant of CtBP1--known as CtBP3 or BARS [Brefeldin A (BFA) ribosylated substrate]--plays a critical role in the fragmentation of the Golgi complex at the onset of mitosis. Although there are some reports of CtBP with a cytoplasmic distribution after transfection, it is unclear how in normal cells a nuclear corepressor regulates the behavior of the Golgi complex at the onset of mitosis. Using polyclonal rabbit antibodies that were raised against a human CtBP1-GST fusion-protein, here we show by immunofluorescence laser-scanning confocal microscopy that in mitotic cells a species of CtBP becomes associated with the centrosomes at the onset of prophase and then throughout mitosis. The association can be seen in both cycling mitotic cells and nocodazole-arrested cells. The interaction was confirmed by coimmunoprecipitation and centrosome isolation. Since centrosomes are considered to be the organising centre for Golgi morphogenesis, the interaction demonstrated here may explain how a nuclear corepressor of transcription can exert a regulatory effect on the Golgi complex at a specific stage of the cell cycle.
CtBP是一种转录共抑制因子，其作用方式是抑制共激活因子，并通过与DNA结合转录因子相互作用，招募一组可修饰组蛋白、抑制转录并使基因表达沉默的蛋白质复合物至启动子控制元件。有两个高度同源的基因CtBP1和CtBP2编码CtBP。此外，还描述了一种与CtBP1相关的蛋白质，其N端比CtBP1少11个氨基酸。这种CtBP1变体——称为CtBP3或BARS[布雷菲德菌素A（BFA）核糖基化底物]——在有丝分裂开始时高尔基体复合物的碎片化过程中起关键作用。尽管有一些关于转染后CtBP呈细胞质分布的报道，但尚不清楚在正常细胞中，一种核共抑制因子如何在有丝分裂开始时调节高尔基体复合物的行为。我们使用针对人CtBP1-GST融合蛋白产生的多克隆兔抗体，通过免疫荧光激光扫描共聚焦显微镜显示，在有丝分裂细胞中，一种CtBP在前期开始时与中心体结合，然后在整个有丝分裂过程中都如此。在循环有丝分裂细胞和诺考达唑阻滞的细胞中均可见这种结合。通过免疫共沉淀和中心体分离证实了这种相互作用。由于中心体被认为是高尔基体形态发生的组织中心，此处所示的相互作用可能解释了转录核共抑制因子如何在细胞周期的特定阶段对高尔基体复合物发挥调节作用。
