Fuentes G M, Rodríguez-Rodríguez L, Palaniappan C, Fay P J, Bambara R A
Department of Microbiology & Immunology, University of Rochester, School of Medicine and Dentistry, New York 14642, USA.
J Biol Chem. 1996 Jan 26;271(4):1966-71. doi: 10.1074/jbc.271.4.1966.
According to the current model for retroviral replication, strand displacement of the long terminal repeat (LTR) is a necessary step during plus strand DNA synthesis in vivo. We have investigated the ability of human immunodeficiency virus reverse transcriptase (HIV-RT) to synthesize in vitro over a 634-nucleotide HIV LTR DNA template, having or lacking a single full-length DNA downstream primer. The presence of the downstream primer resulted in an approximately 12-fold reduction in the rate of upstream primer elongation. Addition of Escherichia coli single-stranded binding protein (SSB) or human replication protein A (RP-A) enhanced strand displacement synthesis; however, addition of HIV nucleocapsid protein (NC) did not. The presence of excess single-stranded DNA complementary to the downstream primer did not stimulate displacement synthesis. Interestingly, we observed that the elongating upstream primer could readily transfer to this DNA. This observation suggests that recombination is favored during strand displacement synthesis in vivo.
根据当前的逆转录病毒复制模型，长末端重复序列（LTR）的链置换是体内正链DNA合成过程中的一个必要步骤。我们研究了人类免疫缺陷病毒逆转录酶（HIV-RT）在具有或不具有单个全长DNA下游引物的634个核苷酸的HIV LTR DNA模板上进行体外合成的能力。下游引物的存在导致上游引物延伸速率降低约12倍。添加大肠杆菌单链结合蛋白（SSB）或人类复制蛋白A（RP-A）可增强链置换合成；然而，添加HIV核衣壳蛋白（NC）则没有这种效果。与下游引物互补的过量单链DNA的存在并未刺激置换合成。有趣的是，我们观察到正在延伸的上游引物可以很容易地转移到该DNA上。这一观察结果表明，体内链置换合成过程中有利于重组。
