The reverse transcriptase encoded by the non-LTR retrotransposon R2 is as error-prone as that encoded by HIV-1.
The reverse transcriptase encoded by the non-LTR retrotransposon R2 is as error-prone as that encoded by HIV-1.
复制标题
非 LTR 逆转录转座子 R2 编码的逆转录酶与 HIV-1 编码的逆转录酶一样容易出错。
DOI：
10.1016/j.jmb.2011.02.015
复制
发表时间：
2011
影响因子：
5.6
通讯作者：
Eickbush,ThomasH
中科院分区：
文献类型：
--
作者：
Jamburuthugoda,VaruniK;Eickbush,ThomasH
逆转录酶(RT)由一系列可移动的逆转录元件编码，对基因组的结构和功能有重要影响。真核生物中最丰富的成分是非长末端重复序列(LTR)反转录转座子。在这里，我们比较了家蚕非LTR反转录转座子R2编码的RT与逆转录病毒特征良好的RT所需的dNTP浓度和错误率。令人惊讶的是，R2被发现具有与人类免疫缺陷病毒1型(HIV-1)等慢病毒RTS更相似的特性，而不是与肿瘤逆转录病毒RTS(如小鼠白血病病毒)的特性更相似。与HIV-1RT一样，R2 RT能够在低浓度的dNTP下合成DNA，这表明R2能够在未分裂的细胞中进行逆转录转座。R2 RT还显示了偏向dNTP池中的误掺入水平和M13 LacZα正向突变检测中的复制错误率，类似于HIV-1 RT。正向突变试验中的大部分R2碱基替换是由于DTMP的错误掺入引起的。与HIV-1类似，R2 RT的高错误率似乎是由于它一旦产生就能延长错配的结果。我们认为R2 RT的低保真度是其活性部位/dNTP结合口袋灵活性的副产品，R2利用其活性部位/dNTP结合口袋进行逆转录反应。最后，我们讨论了尽管R2 RT错误率很高，但基于自然群体中R2逆转座的频率，R2的长期核苷酸替换率并不显著高于与细胞DNA复制相关的核苷酸替换率。
Reverse transcriptases (RTs) encoded by a wide range of mobile retroelements have had a major impact on the structure and function of genomes. Among the most abundant elements in eukaryotes are the non long terminal repeat (LTR) retrotransposons. Here we compare the dNTP concentration requirements and error rates of the RT encoded by the non-LTR retrotransposon R2 of Bombyx mori with the well-characterized RTs of retroviruses. Surprisingly, R2 was found to have properties more similar to those of lentiviral RTs, such as human immunodeficiency virus type 1 (HIV-1), than to those of oncoretroviral RTs, such as murine leukemia virus. Like HIV-1 RT, R2 RT was able to synthesize DNA at low dNTP concentrations, suggesting that R2 is able to retrotranspose in nondividing cells. R2 RT also showed levels of misincorporation in biased dNTP pools and replication error rates in M13 lacZα forward mutation assays, similar to HIV-1 RT. Most of the R2 base substitutions in the forward mutation assay were caused by the misincorporation of dTMP. Analogous to HIV-1, the high error rate of R2 RT appears to be a result of its ability to extend mismatches once generated. We suggest that the low fidelity of R2 RT is a by-product of the flexibility of its active site/dNTP binding pocket required for the target-primed reverse transcription reaction used by R2 for retrotransposition. Finally, we discuss that in spite of the high R2 RT error rate, the long-term nucleotide substitution rate for R2 is not significantly above that associated with cellular DNA replication, based on the frequency of R2 retrotranspositions determined in natural populations.