大肠杆菌染色体复制起始调控  

Control of Initiation of Chromosomal Replication in Escherichia coli

作　　者：莫日根[1] 怡荣[1] 

机构地区：[1]内蒙古大学生命科学学院,呼和浩特010021

出　　处：《内蒙古大学学报（自然科学版）》2012年第4期439-448,共10页Journal of Inner Mongolia University：Natural Science Edition

基　　金：国家自然科学基金资助项目(31060015);内蒙古自然科学基金重点项目(2010Zd14);内蒙古大学人才引进科研启动基金资助项目(SPH-IMU;Z20090107)

摘　　要：大肠杆菌染色体具唯一一个复制原点叫oriC.在oriC上染色体的复制起始是个严格控制的细胞过程.首先,复制起始蛋白DnaA与oriC上DnaA框相互作用,使DNA分子弯曲,并在IHF和HU等蛋白的帮助下,使oriC双链DNA在其富含AT区解链,便起始复制.DnaA蛋白有两种形式,即ATP-DnaA和ADP-DnaA,前者有复制起始活性,后者则没有.DnaA蛋白浓度的提高和由DRAS使ADP-DnaA激活为ATP-DnaA都会导致额外的复制起始,说明ATP-DnaA是个复制起始正调控因子.DiaA蛋白通过与ATP-DnaA的相互作用来促使ATP-DnaA-oriC复合物的形成,从而激发复制起始.然而,在每个细胞周期中,DNA复制起始只发生一次.有不同的分子机制抑制在同一个细胞周期的同一复制原点上重复起始复制.1)复制原点的隔绝防止复制起始.由SeqA蛋白结合在oriC中半甲基化的多个GATC位点,使oriC失去复制起始活性;2)由RIDA使ATP-DnaA降解为ADP-DnaA,使DnaA失去复制起始活性;3)Dps蛋白抑制依赖DnaA蛋白的oriC解链;4)datA序列通过降低作用于oriC的DnaA可用量来延缓复制起始时间.显然,一个复杂的调控网络控制着复制起始.本文回顾、总结和分析了大肠杆菌复制起始调控机制.Escherichia coli is a prokaryotic organism of single cells with a chromosome of circular double-stranded DNA.Chromosomal replication initiates from a single site called oriC.The initiation of replication at oric is precisely regulated.The first event of initiation is that the DnaA protein binds to DnaA-boxes and subsequently bends the DNA of oriC.With the help of IHF and HU proteins,DnaA induces the separation of DNA strands at the AT-rich region,and starts initiation.DnaA protein binds ATP or ADP to form ATP-DnaA or ADP-DnaA.ATP-DnaA is active for initiation of replication while ADP-DnaA is inactive.An increase in concentration of the DnaA protein,and reactivation of ADP-DnaA to ATP-DnaA results in overinitiation.This indicates that ATP-DnaA is a positive regulatory factor.DiaA protein stimulates formation of initiation complex of ATP-DnaA-oriC.However,each origin initiates only once per cell cycle.There are different molecular processes inhibit the reinitiation of replication at each origin in one cell cycle.1)Sequestration of oriC:SeqA protein binds to hemimethylated GATC sites,inactivating the oriC for initiation of replication;2)RIDA induces hydrolysis of active ATP-DnaA to inactive ADP-DnaA;3)Dps protein prevents DnaA dependent unwinding of oriC through interacting with DnaA;4)the datA locus binds a large amount of DnaA,leading to a delay of replication initiation.In this paper,we reviewed the regulation mechanisms of replication initiation in E.coli.

关 键 词：复制起始 调控网络 大肠杆菌 

分 类 号：Q933[生物学—微生物学]