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. 2020 May;594(9):1359-1367.
doi: 10.1002/1873-3468.13738. Epub 2020 Feb 9.

Resolution of ROS-induced G-quadruplexes and R-loops at transcriptionally active sites is dependent on BLM helicase

Jun Tan  1   2 , Xiangyu Wang  1   2 , Laiyee Phoon  1   2 , Haibo Yang  1   2 , Li Lan  1   2
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Free article

Resolution of ROS-induced G-quadruplexes and R-loops at transcriptionally active sites is dependent on BLM helicase

Jun Tan et al. FEBS Lett. 2020 May.
Free article

Abstract

R-loops and G-quadruplexes (G4s) are noncanonical secondary DNA structures. Here, we show that reactive oxygen species (ROS) induce G4 formation as well as R-loops at transcriptionally active sites. Importantly, the G4 structure is subsequently triggered by R-loop formation after damage. Once G4 is formed within an R-loop, it reversely stabilizes the R-loop. Notably, the helicase activity of Bloom syndrome protein is essential for the resolution of both R-loops and G4s. Unresolved G4s and R-loops delay the repair of ROS-induced damage at actively transcribed sites. Together, our results demonstrate that interregulation between R-loops and G4s induced by ROS is essential for repair at transcriptionally active sites.

Keywords: BLM helicase; DNA damage repair; G-quadruplex; R-loop; ROS; transcription.

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