A bacterial PrimPol-reverse transcriptase hybrid protein has a proofreading exonuclease activity that can be transferred to other reverse transcriptases

作者：S. Kim, Hengyi Xu, Georg Mohr, Jun Yao, Yan Zhang, Guzhen Cui, Alan M. Lambowitz · 发表于：bioRxiv (Cold Spring Harbor Laboratory) · 年份：2025 · DOI：10.1101/2025.09.07.674619 · 被引用次数：4 · 研究领域：DNA Repair Mechanisms、DNA and Nucleic Acid Chemistry、Bacterial Genetics and Biotechnology

PPRT protein, which has an N-terminal Primase-Polymerase (PrimPol) domain fused to a group II intron-like reverse transcriptase (RT) domain followed by a long C-terminal domain (CTD), contributes to a cellular oxidative DNA damage response in addition to its previously described function in phage defense. Biochemical analysis showed that the PrimPol domain has an error-prone DNA polymerase activity that enables read through of oxidation-induced DNA damage. Surprisingly, we found that the RT-like domain, in addition to synthesizing protein-primed DNAs for phage defense, has a 3' to 5' DNA exonuclease activity that functions in proofreading DNAs synthesized by the PrimPol domain. Extending these findings, we identified structural features that contribute to this proofreading activity, enabling us to associate it with both a group II intron-encoded and retroviral RT and suggesting general methods for incorporating proofreading activity into RTs.