Replication protein A plays multifaceted roles complementary to specialized helicases in processing G-quadruplex DNA
Yi-Ran Wang,
Ting-Ting Guo,
Ya-Ting Zheng,
Chang-Wei Lai,
Bo Sun,
Xu-Guang Xi,
Xi-Miao Hou
Affiliations
Yi-Ran Wang
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
Ting-Ting Guo
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
Ya-Ting Zheng
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
Chang-Wei Lai
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
Bo Sun
School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
Xu-Guang Xi
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China; LBPA, Ecole Normale Supérieure Paris-Saclay, CNRS, Gif-sur-Yvette, France
Xi-Miao Hou
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China; Corresponding author
Summary: G-quadruplexes (G4s) are non-canonical DNA structures with critical roles in DNA metabolisms. To resolve those structures that can cause replication fork stalling and genomic instability, single-stranded DNA-binding proteins and helicases are required. Here, we characterized the interplay between RPA and helicases on G4s using single-molecule FRET. We first discovered that human RPA efficiently prevents G4 formation by preempting ssDNA before its folding. RPA also differentially interacts with the folded G4s. However, helicases such as human BLM and yeast Pif1 have different G4 preferences from RPA mainly based on loop lengths. More importantly, both RPA and these helicases are required for the stable G4 unfolding, as RPA promotes helicase-mediated repetitive unfolding into durative linear state. Furthermore, BLM can traverse G4 obstacles temporarily disrupted by RPA and continue to unwind downstream duplex. We finally proposed the mechanisms underlying above functions of RPA in preventing, resolving, and assisting helicases to eliminate G4s.
