Li Feng, Lee Michael, Esnault Caroline, Wendover Katie, Guo Yabin, Atkins Paul, Zaratiegui Mikel, Levin Henry L
Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Bioinformatics and Scientific Programming Core, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Sci Adv. 2022 Jul;8(26):eabm9390. doi: 10.1126/sciadv.abm9390. Epub 2022 Jun 29.
Retroviruses and long terminal repeat retrotransposons rely on integrase (IN) to insert their complementary DNA (cDNA) into the genome of host cells. Nevertheless, in the absence of IN, retroelements can retain notable levels of insertion activity. We have characterized the IN-independent pathway of Tf1 and found that insertion sites had homology to the primers of reverse transcription, which form single-stranded DNAs at the termini of the cDNA. In the absence of IN activity, a similar bias was observed with HIV-1. Our studies showed that the Tf1 insertions result from single-strand annealing, a noncanonical form of homologous recombination mediated by Rad52. By expanding our analysis of insertions to include repeat sequences, we found most formed tandem elements by inserting at preexisting copies of a related transposable element. Unexpectedly, we found that wild-type Tf1 uses the IN-independent pathway as an alternative mode of insertion.
逆转录病毒和长末端重复逆转座子依靠整合酶（IN）将其互补DNA（cDNA）插入宿主细胞基因组。然而，在缺乏整合酶的情况下，逆转元件仍可保持显著水平的插入活性。我们已对Tf1的不依赖整合酶途径进行了表征，并发现插入位点与逆转录引物具有同源性，这些引物在cDNA末端形成单链DNA。在缺乏整合酶活性的情况下，HIV-1也观察到类似的偏向性。我们的研究表明，Tf1插入是由单链退火导致的，这是一种由Rad52介导的非经典同源重组形式。通过将插入分析扩展至包括重复序列，我们发现大多数通过插入相关转座元件的现有拷贝而形成串联元件。出乎意料的是，我们发现野生型Tf1将不依赖整合酶途径用作一种替代插入模式。
