Penno Christophe, Kumari Romika, Baranov Pavel V, van Sinderen Douwe, Atkins John F
School of Biochemistry, University College Cork, Cork, Ireland.
School of Microbiology, University College Cork, Cork, Ireland.
Nucleic Acids Res. 2017 Sep 29;45(17):10156-10167. doi: 10.1093/nar/gkx690.
Synthesis of HIV GagPol involves a proportion of ribosomes translating a U6A shift site at the distal end of the gag gene performing a programmed -1 ribosomal frameshift event to enter the overlapping pol gene. In vitro studies here show that at the same shift motif HIV reverse transcriptase generates -1 and +1 indels with their ratio being sensitive to the relative concentration ratio of dNTPs specified by the RNA template slippage-prone sequence and its 5' adjacent base. The GGG sequence 3' adjacent to the U6A shift/slippage site, which is important for ribosomal frameshifting, is shown here to limit reverse transcriptase base substitution and indel 'errors' in the run of A's in the product. The indels characterized here have either 1 more or less A, than the corresponding number of template U's. cDNA with 5 A's may yield novel Gag product(s), while cDNA with an extra base, 7 A's, may only be a minor contributor to GagPol polyprotein. Synthesis of a proportion of non-ribosomal frameshift derived GagPol would be relevant in efforts to identify therapeutically useful compounds that perturb the ratio of GagPol to Gag, and pertinent to the extent in which specific polymerase slippage is utilized in gene expression.
HIV GagPol的合成涉及一定比例的核糖体，这些核糖体翻译gag基因末端的U6A移码位点，通过程序性-1核糖体移码事件进入重叠的pol基因。本文的体外研究表明，在相同的移码基序下，HIV逆转录酶会产生-1和+1插入缺失，其比例对RNA模板易滑动序列及其5'相邻碱基所指定的dNTP相对浓度比敏感。U6A移码/滑动位点3'相邻的GGG序列对核糖体移码很重要，本文表明它能限制逆转录酶在产物A序列中的碱基替换和插入缺失“错误”。本文所表征的插入缺失比相应模板U的数量多一个或少一个A。含有5个A的cDNA可能产生新的Gag产物，而含有额外一个碱基（7个A）的cDNA可能只是GagPol多蛋白的次要来源。合成一定比例非核糖体移码衍生的GagPol，对于鉴定扰乱GagPol与Gag比例的治疗有用化合物的研究具有重要意义，也与基因表达中特定聚合酶滑动的利用程度相关。
