title: Involvement of molecular chaperonins in nucleotide excision repair. Dnak leads to increased thermal stability of UvrA, catalytic UvrB loading, enhanced repair, and increased UV resistance.
abstract: UvrA is one of the key Escherichia coli proteins involved in removing DNA damage during the process of nucleotide excision repair. The relatively low concentrations (nanomolar) of the protein in the normal cells raise the potential questions about its stability in vivo under both normal and stress conditions. In vitro, UvrA at low concentrations is shown to be stabilized to heat inactivation by E. coli molecular chaperones DnaK or the combination of DnaK, DnaJ, and GrpE. These chaperone proteins allow sub-nanomolar concentrations of UvrA to load UvrB through >10 cycles of incision. Guanidine hydrochloride-denatured UvrA was reactivated by DnaK, DnaJ, and GrpE to as much as 50% of the native protein activity. Co-immunoprecipitation assays showed that DnaK bound denatured UvrA in the absence of ATP. UV survival studies of a DnaK-deficient strain indicated an 80-fold increased sensitivity to 100 J/m2 of ultraviolet light (254 nm) as compared with an isogenic wild-type strain. Global repair analysis indicated a reduction in the extent of pyrimidine dimer and 6-4 photoproduct removal in the DnaK-deficient cells. These results suggest that molecular chaperonins participate in nucleotide excision repair by maintaining repair proteins in their properly folded state.
authors.affiliation: Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, Texas 77555-1071, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zou
authors.forename: D J
authors.initials: DJ
authors.lastname: Crowley
authors.forename: B
authors.initials: B
authors.lastname: Van Houten
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D004265:DNA Helicases; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D007700:Kinetics; D018832:Molecular Chaperones / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; C058093:UvrB protein, E coli; C068631:UvrA protein, E coli; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli; D004265:DNA Helicases