title: Mechanical force antagonizes the inhibitory effects of RecX on RecA filament formation in Mycobacterium tuberculosis.
abstract: Efficient bacterial recombinational DNA repair involves rapid cycles of RecA filament assembly and disassembly. The RecX protein plays a crucial inhibitory role in RecA filament formation and stability. As the broken ends of DNA are tethered during homologous search, RecA filaments assembled at the ends are likely subject to force. In this work, we investigated the interplay between RecX and force on RecA filament formation and stability. Using magnetic tweezers, at single molecular level, we found that Mycobacterium tuberculosis (Mt) RecX could catalyze stepwise de-polymerization of preformed MtRecA filament in the presence of ATP hydrolysis at low forces (<7 pN). However, applying larger forces antagonized the inhibitory effects of MtRecX, and a partially de-polymerized MtRecA filament could re-polymerize in the presence of MtRecX, which cannot be explained by previous models. Theoretical analysis of force-dependent conformational free energies of naked ssDNA and RecA nucleoprotein filament suggests that mechanical force stabilizes RecA filament, which provides a possible mechanism for the observation. As the antagonizing effect of force on the inhibitory function of RecX takes place in a physiological range; these findings broadly suggest a potential mechanosensitive regulation during homologous recombination.
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Shimin
authors.initials: S
authors.lastname: Le
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, Xiamen University, Xiamen 361005, China.
authors.forename: Hu
authors.initials: H
authors.lastname: Chen
authors.affiliation: BioSystems and Micromechanics (BioSyM) IRG, Singapore-MIT Alliance for Research and Technology, National University of Singapore, Singapore 138602, Singapore.
authors.forename: Xinghua
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India.
authors.forename: K Neelakanteshwar
authors.initials: KN
authors.lastname: Patil
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India phyyj@nus.edu.sg.
authors.forename: Kalappa
authors.initials: K
authors.lastname: Muniyappa
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore Centre for Bioimaging Sciences, National University of Singapore, Singapore 117557, Singapore phyyj@nus.edu.sg.
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001696:Biomechanical Phenomena; D004277:DNA, Single-Stranded; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D058105:Polymerization; D011938:Rec A Recombinases / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D000255:Adenosine Triphosphate; D011938:Rec A Recombinases