Specific amino acid residues in the beta sliding clamp establish a DNA polymerase usage hierarchy in Escherichia coli

DNA Repair (Amst). 2006 Mar 7;5(3):312-23. doi: 10.1016/j.dnarep.2005.10.011. Epub 2005 Dec 9.


Escherichia coli dnaN159 strains encode a mutant form of the beta sliding clamp (beta159), causing them to display altered DNA polymerase (pol) usage. In order to better understand mechanisms of pol selection/switching in E. coli, we have further characterized pol usage in the dnaN159 strain. The dnaN159 allele contains two amino acid substitutions: G66E (glycine-66 to glutamic acid) and G174A (glycine-174 to alanine). Our results indicated that the G174A substitution impaired interaction of the beta clamp with the alpha catalytic subunit of pol III. In light of this finding, we designed two additional dnaN alleles. One of these dnaN alleles contained a G174A substitution (beta-G174A), while the other contained D173A, G174A and H175A substitutions (beta-173-175). Examination of strains bearing these different dnaN alleles indicated that each conferred a distinct UV sensitive phenotype that was dependent upon a unique combination of Delta polB (pol II), Delta dinB (pol IV) and/or Delta umuDC (pol V) alleles. Taken together, these findings indicate that mutations in the beta clamp differentially affect the functions of these three pols, and suggest that pol II, pol IV and pol V are capable of influencing each others' abilities to gain access to the replication fork. These findings are discussed in terms of a model whereby amino acid residues in the vicinity of those mutated in beta159 (G66 and G174) help to define a DNA polymerase usage hierarchy in E. coli following UV irradiation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Amino Acids / genetics
  • Amino Acids / metabolism*
  • DNA Polymerase II / genetics
  • DNA Polymerase II / metabolism*
  • DNA Polymerase II / radiation effects
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / metabolism*
  • DNA Polymerase beta / radiation effects
  • DNA Replication
  • DNA, Bacterial / biosynthesis
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • DNA-Directed DNA Polymerase / radiation effects
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Proteins
  • Gene Expression Regulation, Bacterial
  • Models, Molecular
  • Mutation
  • Phenotype
  • Ultraviolet Rays


  • Amino Acids
  • DNA, Bacterial
  • Escherichia coli Proteins
  • DNA Polymerase II
  • DNA Polymerase beta
  • DNA polymerase V, E coli
  • DNA-Directed DNA Polymerase