title: Mycobacterium tuberculosis UvrD1 and UvrA proteins suppress DNA strand exchange promoted by cognate and noncognate RecA proteins.
abstract: DNA helicases are present in all kingdoms of life and play crucial roles in processes of DNA metabolism such as replication, repair, recombination, and transcription. To date, however, the role of DNA helicases during homologous recombination in mycobacteria remains unknown. In this study, we show that Mycobacterium tuberculosis UvrD1 more efficiently inhibited the strand exchange promoted by its cognate RecA, compared to noncognate Mycobacterium smegmatis or Escherichia coli RecA proteins. The M. tuberculosis UvrD1(Q276R) mutant lacking the helicase and ATPase activities was able to block strand exchange promoted by mycobacterial RecA proteins but not of E. coli RecA. We observed that M. tuberculosis UvrA by itself has no discernible effect on strand exchange promoted by E. coli RecA but impedes the reaction catalyzed by the mycobacterial RecA proteins. Our data also show that M. tuberculosis UvrA and UvrD1 can act together to inhibit strand exchange promoted by mycobacterial RecA proteins. Taken together, these findings raise the possibility that UvrD1 and UvrA might act together in vivo to counter the deleterious effects of RecA nucleoprotein filaments and/or facilitate the dissolution of recombination intermediates. Finally, we provide direct experimental evidence for a physical interaction between M. tuberculosis UvrD1 and RecA on one hand and RecA and UvrA on the other hand. These observations are consistent with a molecular mechanism, whereby M. tuberculosis UvrA and UvrD1, acting together, block DNA strand exchange promoted by cognate and noncognate RecA proteins.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Pawan
authors.initials: P
authors.lastname: Singh
authors.forename: K Neelakanteshwar
authors.initials: KN
authors.lastname: Patil
authors.forename: Jasbeer Singh
authors.initials: JS
authors.lastname: Khanduja
authors.forename: P Sanjay
authors.initials: PS
authors.lastname: Kumar
authors.forename: Alan
authors.initials: A
authors.lastname: Williams
authors.forename: Franca
authors.initials: F
authors.lastname: Rossi
authors.forename: Menico
authors.initials: M
authors.lastname: Rizzi
authors.forename: Elaine O
authors.initials: EO
authors.lastname: Davis
authors.forename: K
authors.initials: K
authors.lastname: Muniyappa
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D020102:Mycobacterium smegmatis / Q000201:enzymology / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D011938:Rec A Recombinases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011995:Recombination, Genetic; D040681:Structural Homology, Protein
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases; D004706:Endodeoxyribonucleases; D004265:DNA Helicases