Mechanical force antagonizes the inhibitory effects of RecX on RecA filament formation in Mycobacterium tuberculosis.
Bottom Line: 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.
Affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore.Show MeSH
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Mentions: To determine how a preformed MtRecA filament is regulated when MtRecX is added to the MtRecA reaction solution, we investigated the effects of MtRecX on the dynamics of disassembly of preformed MtRecA filaments. At low concentrations of MtRecX (80 nM), we observed progressive reductions in DNA extension at ∼3 pN (Figure 2A), indicating net MtRecA filament disassembly. Although noisy, the disassembly process appeared stepwise overall. In addition to the dominant disassembly process, occasionally large step (> 10 nm) MtRecA re-assembly events were also observed (arrows, Figure 2A).
Affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore.