Function of NudC, a Prolactin Regulated Gene

描述（由申请人提供）：垂体激素催乳素（PRL）刺激许多组织和细胞类型的生长和分化。为了了解PRL在促有丝分裂信号传导中的作用，我们分离了一些PRL刺激后激活的立即早期基因。其中一个基因NudC被克隆为早期生长反应基因。遗传学、生物化学和细胞学研究表明，NudC与微管（MT）依赖的动力蛋白/动力肌动蛋白运动复合体相关，该复合体介导许多有丝分裂过程。我们的研究表明，NudC在有丝分裂（核分裂）和胞质分裂（胞质分裂）中起着多种作用。我们发现，通过小干扰RNA（siRNA）介导的基因沉默或腺病毒介导的过表达改变NudC水平导致胞质分裂缺陷，这反映在多核细胞和具有持续细胞间连接的细胞数量增加。中间区和中间体基质中的MT出现紊乱，为胞质分裂缺陷提供了可能的线索。此外，我们发现NudC是一种有丝分裂磷蛋白，它与有丝分裂激酶polo样激酶1（Plkl）相互作用，这表明NudC磷酸化可能会影响NudC在有丝分裂过程中的功能。我们假设，一个精确的水平和磷酸化状态的NudC需要有丝分裂的进展和完成的胞质分裂，NudC的功能，通过调节动力蛋白/动力肌动蛋白复合物和MT动力学在有丝分裂和胞质分裂。为了描述NudC在促有丝分裂信号传导中的功能，我们建议1）通过分析NudC水平和磷酸化状态的变化如何影响有丝分裂进程和胞质分裂的完成来确定NudC在有丝分裂和胞质分裂中的功能，以及2）通过解决NudC如何调节动力蛋白复合物稳定性和MT动力学来分析NudC对动力蛋白/动力肌动蛋白的调节。这些研究将有助于从根本上了解PRL介导的促有丝分裂信号的机制。

DESCRIPTION (provided by applicant): The pituitary hormone prolactin (PRL) stimulates the growth and differentiation of many tissues and cell types. To understand a role of PRL in mitogenic signaling, we isolated a number of immediate early genes activated after PRL stimulation. One such gene, NudC, was cloned as an early growth response gene. Genetic, biochemical and cellular studies show that NudC associates with the microtubule (MT)-dependent dynein/dynactin motor complex that mediates many mitotic processes. Our studies suggest that NudC plays multiple roles in mitosis (nuclear division) and cytokinesis (cytoplasmic division). We showed that altering NudC levels by either small interference RNA (siRNA)-mediated gene silencing or adenovirus-mediated overexpression resulted in defects in cytokinesis, as reflected by an increase in the number of multinucleated cells and cells with persistent intercellular connections. MTs in the midzone and midbody matrix appeared disorganized, providing a possible clue on a cytokinesis defect. In addition, we show that NudC is a mitotic phosphoprotein and it interacts with the mitotic kinase polo-like kinase 1 (Plkl), suggesting that NudC phosphorylation may affect NudC functions during mitosis. We hypothesize that a precise level and phosphorylation state of NudC are required for mitotic progression and completion of cytokinesis, and that NudC functions by regulating the dynein/dynactin complex and MT dynamics during mitosis and cytokinesis. To delineate NudC functions in mitogenic signaling, we propose to 1) Determine NudC function in mitosis and cytokinesis by analyzing how changes in NudC levels and phosphorylation state affect mitosis progression and completion of cytokinesis, and to 2) Analyze regulation of dynein/dynactin by NudC by addressing how NudC regulates dynein complex stability and MT dynamics. These studies should contribute to a fundamental understanding of the mechanisms of PRL-mediated mitogenic signaling.