Effects of cdc2 gene and EMC tenasc in on regulation of growth and differentiation of hematopoietic cells

我们最近的研究工作取得了以下结果：(1)在未成熟的骨髓细胞中很容易检测到cdc2mRNA的转录本，并随着细胞周期的停止而变得检测不到：在粒细胞分化的髓/中粒细胞阶段之后，检测不到它。外周血粒细胞、单核细胞和T淋巴细胞等静息细胞不表达cdc2基因转录本。在特定的有丝分裂原如PHA的刺激下，T淋巴细胞在重新进入细胞周期时可诱导CDc2mRNA的表达，而粒细胞和单核细胞即使在适当的刺激条件下也不能诱导CDc2mRNA的表达。在T淋巴细胞中，即使在有丝分裂刺激诱导cdc2基因表达后，也没有观察到染色质结构的变化，如DNA酶I超敏部位的出现或DNA甲基化状态的改变。然后，我们通过连接介导的聚合酶链式反应分离了cdc2基因的调控序列，发现E2F结合位点位于NT-117到-124，Rb调控元件位于NT-106到-112和-156到-165。(2)Tenascin是一种新的六臂细胞外基质糖蛋白，表达与间充质-上皮细胞相互作用有关，其表达在细胞发生和癌变过程中受到时间限制。免疫沉淀研究显示，两个腹水-肝癌来源的细胞系和一个肉瘤来源的细胞系在体外合成了Tenascin。其他被检测的细胞系，包括所有来自正常肝细胞的细胞系，Tenascin的表达都是阴性的。在上皮性和非上皮性细胞系之间进行共培养研究。细胞共培养后，Tenascin的表达没有明显变化。作为体内研究，将细胞系移植到裸鼠体内。所有上皮系的异种移植都与一种

Our recent research works brought about the following results : (1) Cdc2 mRNA transcript wasreadily detected in immature bone marrow cells and became undetectable accompanying with the cell cycle arrest which ocurred along wich differentiation : it was undetectable after the myelocyte/metamyelocyte stages in granulocytic differentiation. Peripheral blood resting cells including granulocytes, monocytes and T-lymphocytes did not express cdc2 mRNA transcripts. Cdc2 mRNA could be induced in T-lymphocytes when the cells re-entered the cell cycle in response to specific mitogens such as PHA.In contrast, cdc2 mRNA could not be induced in granulocytes and monocytes even after the culture with the appropriate stimulants such as LPS or CSFs. The changes in the chromatin structure such as the appearance of DNase I hypersensitivity sites or the slteration of DNA methylation status were not observed in T-lymphocytes even after the induction of cdc2 mRNA expression by mitogenic stimuli. Then, we isolated the regulatory sequence of cdc2 gene by a ligation-mediated PCR and found E2F binding site at the position of nt -117 to -124 and the RB control elements at the positions of nt -106 to -112 and -156 to -165. (2) Tenascin is a novel six-armed extracellular-matrix glycoprotein expressed in association with mesenchymal-epithelial interactions, and its expression is temporally restricted during oganogenesis and carcinogenesis. Immuoprecipitation studies revealed two ascites-hepatoma-derived cell lines and one sarcoma-derived line synthesized tenascin in vitro. The other cell lines examined, including all of those derived from normal hepatocytes, were negative for the expression of tenascin. Coculture studies were performed between epithelial and nonepithelial cell lines. No drastic change in tenascin expression was found after cocultuing the cells. As an in vivo study, cell lines were transplanted into nude mice. All xenografts of the epithelial lines were associated with a storong