A single domain in human DNA polymerase iota mediates interaction with PCNA: implications for translesion DNA synthesis

Mol Cell Biol. 2005 Feb;25(3):1183-90. doi: 10.1128/MCB.25.3.1183-1190.2005.


DNA polymerases (Pols) of the Y family rescue stalled replication forks by promoting replication through DNA lesions. Humans have four Y family Pols, eta, iota, kappa, and Rev1, of which Pols eta, iota, and kappa have been shown to physically interact with proliferating cell nuclear antigen (PCNA) and be functionally stimulated by it. However, in sharp contrast to the large increase in processivity that PCNA binding imparts to the replicative Pol, Poldelta, the processivity of Y family Pols is not enhanced upon PCNA binding. Instead, PCNA binding improves the efficiency of nucleotide incorporation via a reduction in the apparent K(m) for the nucleotide. Here we show that Poliota interacts with PCNA via only one of its conserved PCNA binding motifs, regardless of whether PCNA is bound to DNA or not. The mode of PCNA binding by Poliota is quite unlike that in Poldelta, where multisite interactions with PCNA provide for a very tight binding of the replicating Pol with PCNA. We discuss the implications of these observations for the accuracy of DNA synthesis during translesion synthesis and for the process of Pol exchange at the lesion site.

Publication types

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

MeSH terms

  • Amino Acid Motifs / physiology
  • Amino Acid Sequence
  • DNA Polymerase III / metabolism*
  • DNA Polymerase iota
  • DNA Replication / physiology*
  • DNA-Directed DNA Polymerase / metabolism*
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Proliferating Cell Nuclear Antigen / metabolism*
  • Protein Binding
  • Recombinant Proteins / metabolism*


  • Proliferating Cell Nuclear Antigen
  • Recombinant Proteins
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase
  • DNA Polymerase iota
  • POLI protein, human