Competitive processivity-clamp usage by DNA polymerases during DNA replication and repair

EMBO J. 2003 Dec 1;22(23):6408-18. doi: 10.1093/emboj/cdg603.


Protein clamps are ubiquitous and essential components of DNA metabolic machineries, where they serve as mobile platforms that interact with a large variety of proteins. In this report we identify residues that are required for binding of the beta-clamp to DNA polymerase III of Escherichia coli, a polymerase of the Pol C family. We show that the alpha polymerase subunit of DNA polymerase III interacts with the beta-clamp via its extreme seven C-terminal residues, some of which are conserved. Moreover, interaction of Pol III with the clamp takes place at the same site as that of the delta-subunit of the clamp loader, providing the basis for a switch between the clamp loading machinery and the polymerase itself. Escherichia coli DNA polymerases I, II, IV and V (UmuC) interact with beta at the same site. Given the limited amounts of clamps in the cell, these results suggest that clamp binding may be competitive and regulated, and that the different polymerases may use the same clamp sequentially during replication and repair.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • DNA Polymerase III / chemistry*
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism*
  • DNA Repair / genetics*
  • DNA Replication / genetics*
  • DNA, Bacterial / genetics
  • Escherichia coli / genetics*
  • Kinetics
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Subunits / chemistry
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism


  • DNA, Bacterial
  • Protein Subunits
  • Recombinant Proteins
  • DNA polymerase III, alpha subunit
  • DNA Polymerase III