Mycobacterium tuberculosis DinG is a structure specific helicase that unwinds G4 DNA: implications for targeting G4 DNA as a novel therapeutic approach [Molecular Bases of Disease]

July 24th, 2014 by Thakur, R. S., Desingu, A., Basavaraju, S., Subramanya, S., Rao, D. N., Nagaraju, G.

The significance of G-quadruplexes and the helicases that resolve G4 structures in prokaryotes is poorly understood. Mycobacterium tuberculosis genome is GC rich and contains 10,000 sequences that have the potential to form G4 structures. In Escherichia coli, RecQ helicase unwinds G4 structures. However, RecQ is absent in M. tuberculosis and the helicase that participates in G4 resolution in M. tuberculosis is obscure. Here, we show that M. tuberculosis DinG (MtDinG) exhibits high affinity for single-stranded DNA (ssDNA) and ssDNA translocation with a 5 to 3 polarity. Interestingly, MtDinG unwinds overhangs, flap structures and forked duplexes but fails to unwind linear duplex DNA. Our data with DNase I footprinting provide mechanistic insights and suggest that MtDinG is a 5 to 3 polarity helicase. Notably, in contrast to E. coli DinG, MtDinG catalyzes unwinding of replication fork and Holliday junction structures. Strikingly, we find that MtDinG resolves intermolecular G4 structures. These data suggest that MtDinG is a multifunctional structure specific helicase that unwinds model structures of DNA replication, repair and recombination as well as G4 structures. We finally demonstrate that promoter sequences of M. tuberculosis PE_PGRS2, mce1R and moeB1 genes contain G4 structures, implying that G4 structures may regulate gene expression in M. tuberculosis. We discuss these data and implicate that targeting G4 structures and DinG helicase in M. tuberculosis could be a novel therapeutic strategy for culminating the infection with this pathogen.
  • Posted in Journal of Biological Chemistry, Publications
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