Hiasa H, Marians K J
Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
J Biol Chem. 1994 Oct 7;269(40):24999-5003.
The effects of the histone-like proteins, HU, IHF, and Fis on DNA replication have been examined in vitro using the oriC and pBR322 DNA replication systems. In the oriC system, although low concentrations of HU and IHF stimulated DNA replication, no stimulation was observed upon the addition of Fis. On the contrary, high concentrations of Fis inhibited oriC DNA replication completely. The inhibitory effect of Fis could be overcome when HU, IHF, or RNA polymerase were also present in the reaction mixtures. Unwinding of duplex DNA at the origin correlated with the elevated level of DNA replication. In contrast, only inhibition, rather than stimulation, was observed when these proteins were added to the pBR322 DNA replication system. Thus, the observed dependence on Fis of oriC DNA replication in vivo cannot be attributed to a positive effect on localized DNA unwinding.
已使用oriC和pBR322 DNA复制系统在体外研究了类组蛋白HU、IHF和Fis对DNA复制的影响。在oriC系统中，尽管低浓度的HU和IHF刺激了DNA复制，但添加Fis后未观察到刺激作用。相反，高浓度的Fis完全抑制了oriC DNA复制。当反应混合物中也存在HU、IHF或RNA聚合酶时，Fis的抑制作用可以被克服。在起始点双链DNA的解旋与DNA复制水平的升高相关。相比之下，当将这些蛋白质添加到pBR322 DNA复制系统中时，仅观察到抑制作用，而非刺激作用。因此，体内观察到的oriC DNA复制对Fis的依赖性不能归因于对局部DNA解旋的积极作用。
