RHAU helicase stabilizes G4 in its nucleotide-free state and destabilizes G4 upon ATP hydrolysis. Nucleic Acids Research, January 2017.

By Huijuan You1, Simon Lattmann2, Daniela Rhodes3, Jie Yan4,5

Nucleic Acids Research. January 2017. 45(1). 206-214. doi: 10.1093/nar/gkw881.

Abstract

The DEAH-box ATP-dependent RHAU helicases specifically unfold RNA and DNA G-quadruplexes (G4s). However, it remains unclear how the RHAU’s G4 unfolding activity is coupled to different stages of the ATPase cycle. Here, using a single-molecule manipulation approach, we show that binding of Drosophila RHAU stabilizes an intramolecularly folded parallel DNA G4 against mechanical unfolding in its nucleotide-free and in its AMP-PNP or ADP bound states, while it destabilizes the G4 when coupled to ATP hydrolysis. Importantly, our results show that the ADP·AlF[Formula: see text]-bound RHAU does not stabilize the G4. We also found that both a single-stranded 3′ DNA tail and the RSM domain of RHAU that binds specifically to the G4 structure, are dispensable for the stabilization of the G4, but both are required for G4 destabilization. Our study provides the first evidence that the unfolding kinetics of a G-quadruplex can be modulated by different nucleotide-bound states of the helicase.

 
1Mechanobiology Institute, National University of Singapore, Singapore.
2NTU Institute of Structural Biology, Nanyang Technological University, Singapore.
3NTU Institute of Structural Biology, Nanyang Technological University, Singapore DRhodes@ntu.edu.sg.
4Mechanobiology Institute, National University of Singapore, Singapore.
5Department of Physics, National University of Singapore, Singapore.