REGULATION OF POLYPLOIDY BY CYTIDYLYLTRANSFERASE (CT)

CTP：磷酸胆碱胞苷转移酶(CT)是限速酶 在CDP-胆碱途径中参与从头合成 胞浆内有磷脂酰胆碱(PC)。然而，超过95%的 CT不是合成PC所必需的，而是存在于细胞核中 未知的原因。最近的研究表明，CT也发挥着重要的作用 在DNA倍性调控中的作用。CT缺乏症可激活 过表达的B细胞淋巴瘤基因2蛋白(Bcl2p)诱导 从二倍体细胞形成稳定的、有活力的四倍体细胞。 CT的表达可抑制四倍体细胞的形成 由Bc l-2p。该提案的长期目标是了解CT如何 参与了基因组复制的调控。我们将测试 假设CT可能有第二种作用，不同于催化 CDP-胆碱的形成，调节基因组复制。第一 特定的目标将决定这种异常的基因组复制 通过以下哪一种机制发生：1)两轮DNA 一个细胞周期合成；2)S两期有丝分裂失败 3)亲本细胞间的细胞融合。第二个具体目标 是为了确定非细胞溶解特性是否对 CT通过研究CT来调节Bc l-2p诱导的基因组复制 缺失突变体缺乏这些特性。第三个具体目标是 测定其对合成CDP的催化活性 胆碱在CT调节基因组复制中起重要作用 催化点突变失活CT突变体的研究 域。在PC合成和基因组调控中都很活跃 复制提示CT可能与细胞协调PC的合成 组织。拟议的研究将提供对1) 肿瘤细胞的多倍体机制；2)细胞与细胞之间的协同作用 倍性调控与PC合成；3)Bcl2新的促进作用 多倍体。更好地理解强调 癌细胞基因组的不稳定性将有助于设计更多 治疗癌症的有效策略。

CTP:phosphocholine cytidylyltransferase (CT) is the rate-limiting enzyme in the CDP-choline pathway for the de novo synthesis of phosphatidylcholine (PC) in the cytoplasm. However over 95 percent of CT is not required for PC synthesis and is present in the nucleus for unknown reasons. Recent studies show that CT also play an important role in the regulation of DNA ploidy. Deficiency of CT can activate the overexpressed B cell lymphoma gene 2 protein (Bcl-2p) to induce the formation of stable and viable tetraploid cells from diplod cells. Expression of CT can suppress the formation of tetraploid cells induced by Bcl-2p. The long-term goal of this proposal is to understand how CT is involved in the regulation of genome duplication. We will test the hypothesis that CT may have a second role, different from catalyzing CDP-choline formation, to regulate the genome duplication. The first specific aim will determine whether this abnormal genome duplication occurs by which one of the following mechanisms: 1) two rounds of DNA synthesis in one cell cycle; 2) failure of mitosis between two S phases or 3) cell fusion between two parental cells. The second specific aim is to determine whether the noncytalytic properties are important for CT to regulate the Bcl-2p-induced genome duplication by studying the CT deletion mutants lacking these properties. The third specific aim will determine whether the catalytic activity for the synthesis of CDP- choline is important for CT in the regulation of genome duplication by studying the inactive CT mutants with point mutation at the catalytic domain. Being active in both PC synthesis and the regulation of genome duplication suggests that CT may coordinate PC synthesis with cell division. The proposed studies will provide insights into 1) the mechanism of polyploidy in cancer cells; 2) the coordination between ploidy control and PC synthesis; 3) a novel role of Bcl-2 in promoting polyploidy. A better understanding of the mechanism that underlines the genome instability in cancer cells will be helpful for designing more efficient strategies of treating cancer.