细胞松驰素B促微丝解聚对DNA合成的作用

利用微丝（ｍｉｃｒｏｆｉｌａｍｅｎｔ，ＭＦ）解聚药物细胞松驰素Ｂ（ｃｙｔｏｃｈａｌａｓｉｎＢ，ＣＢ）处理Ｇ_０期小鼠Ｃ_３Ｈ_（１０）Ｔ_（１／２）成纤维细胞，对Ｇ_０至Ｓ期ＤＮＡ合成，胸腺嘧啶核苷激酶（ｔｈｙｍｉｄｉｎｅｋｉｎａｓｅ，ＴＫ）活性、ＴＫ基因表达、钙调素（ｃａｌｍｏｄｕｌｉｎ，ＣａＭ）水平和一些细胞周期早期基因的表达进行了观察，Ｇ_０期细胞经３ｍｇ／ＬＣＢ处理２ｈ，促ＭＦ解聚增强了血清对Ｓ期细胞ＴＫ活性、ＴＫ基因表达和ＤＮＡ合成的刺激作用，并促进细胞提前进入Ｓ期．血清刺激Ｇ_０期细胞进入晚Ｇ_１期和Ｓ期时，ＣａＭ水平明显升高，而ＣＢ预处理则使ＣａＭ含量进一步增加，特别是ＣＢ处理促使Ｓ期ＣａＭ增加向核内转移．ＣＢ处理明显增强血清对ｃ－ｊｕｎ、ｃ－ｆｏｓ和ｃ－ｍｙｃ基因表达的刺激作用，而ＰＫＣ抑制剂Ｈ_７则抑制ＣＢ处理对这些基因转录的刺激作用，说明ＣＢ使Ｇ_０期细胞ＭＦ解聚刺激ｃ－ｊｕｎ、ｃ－ｆｏｓ和ｃ－ｍｙｃ的转录活性与ＰＫＣ的作用有关．结果表明Ｇ_０至Ｓ期早期ＭＦ的重组可促进细胞进入Ｓ期，增强ＤＮＡ合成．

Effects of Microfilament Depolymerization by Cytochalasin B on DNA Synthesis

It was conducted that by using quiescent C_(13)H_(10)T_(1/2) fibroblasts for studying the role of microfilament (MF) depolymerization in the regulation of progression from G_0 to S phase. Pretreatment fo G_0 cells with the MF destroying agent-cytochalasin B (CB) (3 mg/L) for 2h,evidently accelerated the entry of G_0 cells into S phase and enhanced DNA synthesis by fetal calf serum (FCS). In cells pretreated with CB,the thymidine kinase (TK) activity and the expression of TK gene were enhanced in comparison with those which were not treated with CB. After pretreatmet of G_0 cells with CB,the calmodulin (CaM) levels both in intact cells and nucleus of late G_1 and S cells by FCS were significantly elevated. In cells pretreated with CB,the expression of cjun,c-fos and c-myc was enhanced obviously as compared with those treated by FCS alone. However,the inhibitor of protein kinase C (PKC)-H_7 markedly suppressed the expression of these genes.It indicated that the regulation of the expression of these genes was closely related to the activity of PKC. The expression of c-jun, c-fos,c-myc and CaM level may be important events in the transition from G_0 to S phase and initiation of DNA synthesis. It predicted that these events are intimately involved in the stimulation of cell response to FCS by CB.