DNA repair mediated by endonuclease-independent LINE-1 retrotransposition
Long interspersed elements (LINE-1s) are abundant retro-transposons in mammalian genomes that probably retro-transpose by target site-primed reverse transcription (TPRT). During TPRT, the LINE-1 endonuclease cleaves genomic DNA, freeing a 3’ hydroxyl that serves as a primer for reverse transcription of LINE-1 RNA by LINE-1 reverse transcriptase. The nascent LINE-1 cDNA joins to genomic DNA, generating LINE-1 structural hallmarks such as frequent 5’ truncations, a 3’ poly(A)+ tail and variable-length target site duplications (TSDs). Here we describe a pathway for LINE-1 retrotransposition in Chinese hamster ovary (CHO) cells that acts independently of endonuclease but is dependent upon reverse transcriptase. We show that endonuclease-independent LINE-1 retrotransposition occurs at near-wildtype levels in two mutant cell lines that are deficient in nonhomologous end-joining (NHEJ). Analysis of the pre- and post-integration sites revealed that endonuclease-independent retrotransposition results in unusual structures because the LINE-1s integrate at atypical target sequences, are truncated predominantly at their 3’ ends and lack TSDs. Moreover, two of nine endonuclease-independent retrotranspositions contained cDNA fragments at their 3’ ends that are probably derived from the reverse transcription of endogenous mRNA. Thus, our results suggest that LINE-1s can integrate into DNA lesions, resulting in retrotransposon-mediated DNA repair in mammalian cells.
Publication Source (Journal or Book title)
Morrish, T., Gilbert, N., Myers, J., Vincent, B., Stamato, T., Taccioli, G., Batzer, M., & Moran, J. (2002). DNA repair mediated by endonuclease-independent LINE-1 retrotransposition. Nature Genetics, 31 (2), 159-165. https://doi.org/10.1038/ng898