Revealing the DNA Unwinding Activity and Mechanism of Fork Reversal by RecG While Exposed to Variants of Stalled Replication-fork at Single-Molecular Resolution |
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| Affiliation: | 1. Single Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India;2. Homi Bhaba National Institute, Mumbai, India;1. Indian Institute of Science Education and Research, Pune, India;2. National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India;1. Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;2. University of Texas Southwestern Medical Center, Dallas, TX 75390, USA;3. Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA;1. Instituto Biofisika (UPV/EHU, CSIC) y Dpto. de Bioquímica y Biología Molecular, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Barrio Sarriena S/N, 48940 Leioa, Spain;2. Precision Medicine and Metabolism Lab, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain;3. Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain;4. Fundación Biofísica Bizkaia, Barrio Sarriena S/N, 48940 Leioa, Spain;1. Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Cumming School of Medicine, University of Calgary, Calgary AB T2N 4N1, Canada;2. Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada |
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| Abstract: | RecG, belonging to the category of Superfamily-2 plays a vital role in rescuing different kinds of stalled fork. The elemental mechanism of the helicase activity of RecG with several non-homologous stalled fork structures resembling intermediates formed during the process of DNA repair has been investigated in the present study to capture the dynamic stages of genetic rearrangement. The functional characterization has been exemplified through quantifying the response of the substrate in terms of their molecular heterogeneity and dynamical response by employing single-molecule fluorescence methods. An elevated processivity of RecG is observed for the stalled fork where progression of lagging daughter strand is ahead as compared to that of the leading strand. Through precise alteration of its function in terms of unwinding, depending upon the substrate DNA, RecG catalyzes the formation of Holliday junction from a stalled fork DNA. RecG is found to adopt an asymmetric mode of locomotion to unwind the lagging daughter strand for facilitating formation of Holliday junction that acts as a suitable intermediate for recombinational repair pathway. Our results emphasize the mechanism adopted by RecG during its ‘sliding back’ mode along the lagging daughter strand to be ‘active translocation and passive unwinding’. This also provide clues as to how this helicase decides and controls the mode of translocation along the DNA to unwind. |
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| Keywords: | DNA repair RecG smFRET replication fork |
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