Molecular mechanism of polyamine effect on cell proliferation

多胺与许多生长过程有关。在本课题中，我们对多胺对细胞增殖的影响进行了如下研究：(1)克隆了多胺在大肠杆菌中的转运基因，并测定了其核苷酸序列。腐胺和亚精胺(精胺)转运蛋白的相对分子质量均为28K。对预测蛋白进行序列分析，推测存在10个跨膜蛋白片段。(2)克隆了大肠杆菌多胺诱导蛋白(PI)，并测定了其核苷酸序列。从基因的限制性内切酶图谱和预测的蛋白序列来看，PI蛋白是存在于周质中的寡肽结合蛋白。(3)多胺缺陷细胞的胸苷激酶(TK)活性是正常细胞的17%。研究了多胺促进TK合成的分子机制。TK的合成主要受翻译水平的多胺调节。(4)刀豆蛋白A激活牛淋巴细胞多胺摄取系统，膜电位依赖性多胺转运体的诱导受细胞内亚精胺和精胺水平的调节。从FM3A细胞中分离到一株缺乏多胺转运蛋白的突变体。

Polyamines have been implicated in numerous growth processes. In this project, we have clarified the following things as for the polyamine effect on cell proliferation.(1) Clones for polyamine tgransport genes in Escherichia coli were isolated and their nucleotide sequences were determined. The molecular weight of putrescine and spermidine (spermine) transport proteins was both 28K. Analysis of the sequence of trhe predicted protein suggested the presence of 10 putative transmembrane segments.(2) A clone for polyamine induced (PI) protein of Escherichia coli was isolated and the nucleotide sequence was determined. From the restriction enzyme map of the gene and the sequence of the predicted protein, PI protein was identified as oligopeptide binding protein existing in the periplasm.(3) It was shown that thymidine kinase (TK) activity in polyaminedeficient cells was 17% of the level in normal cells. The molecular mechanism of polyamine stimulation of TK synthesis has been studied. The synthesis of TK was mainly regulated by polyamines at the level of translation.(4) The polyamine uptake system in bovine lymphocytes was activated by concanavalin A. The induction of the membrane-potential-dependent polyamine transporter is regulated by the intracellular level of spermidine and spermine. A mutant lacking polyamine transporter was isolated from FM3A cells.