3+DNA的复制幻灯片.pptVIP

* * * * Replication termini in E. coli are located beyond the point at which the replication forks actually meet. * * U * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 起始因子蛋白的三个功能: (1) binds to replicator, (2) distorts/unwinds a region of DNA, (3) interacts with and recruits additional replication factors DnaA in E. coli (all 3 functions), origin recognition complex (ORC) in eukaryotes (functions 1 3) 蛋白质和蛋白质及蛋白和DNA的相互作用指导了起始过程 Binding and unwinding DnaA recruits(募集)the DNA helicase DnaB and the helicase loader DnaC DnaB interacts with primase to initiate RNA primer synthesis. Eukaryotic chromosome are replicated exactly once per cell cycle, which is critical for these organims Binding and unwinding Pre-replicative complex (pre-RC) formation directs the initiation of replication in eukaryotes Binding and unwinding Initiation in eukaryotes requires two distinct steps Replicator selection: the process of identifying sequences for replication initiation (G1 phase), which is mediated by the formation of pre-RCs at the replicator region. pre-RC formation Origin activation: pre-RCs are activated by two protein kinases (Cdk and Ddk) that are active only when the cells enter S phase. pre-RC activation assembly of the replication fork in eukaryotes Pre-RC formation and activation is regulated to allow only a single round of replication during each cell cycle. Binding and unwinding Only one opportunity for pre-RCs to form, and only one opportunity for pre-RC activation. Effect of Cdk activity on pre-RC formation and activation Cell cycle regulation of Cdk activity and pre-RC formatin 复制终止 1、环形DNA复制的终止 a、终止序列 E.coli 有两个终止区域，分别结合专一性的终 止蛋白 序列一：terE terD terA 序列二：terF terB terC 每个区域只对一个方向的复制叉起作用 b、专一性终止蛋白 E.coli 中由 tus gene 编码 通过抑制DNA螺旋酶而发挥终止作用 每次复制时只使用一个终止位点 ter 2 染色