The Pol32 subunit of DNA polymerase delta contains separable domains for processive replication and proliferating cell nuclear antigen (PCNA) binding

J Biol Chem. 2004 Jan 16;279(3):1907-15. doi: 10.1074/jbc.M310362200. Epub 2003 Oct 31.


We have carried out a domain analysis of POL32, the third subunit of Saccharomyces cerevisiae DNA polymerase delta (Pol delta). Interactions with POL31, the second subunit of Pol delta, are specified by the amino-terminal 92 amino acids, whereas interactions with the replication clamp proliferating cell nuclear antigen (PCNA, POL30) reside at the extreme carboxyl-terminal region. Pol32 binding, in vivo and in vitro, to the large subunit of DNA polymerase alpha, POL1, requires the carboxyl-proximal region of Pol32. The amino-terminal region of Pol32 is essential for damage-induced mutagenesis. However, the presence of its carboxyl-terminal PCNA-binding domain enhances the efficiency of mutagenesis, particularly at high loads of DNA damage. In vitro, in the absence of effector DNA, the PCNA-binding domain of Pol32 is essential for PCNA-Pol delta interactions. However, this domain has minimal importance for processive DNA synthesis by the ternary DNA-PCNA-Pol delta complex. Rather, processivity is determined by PCNA-binding domains located in the Pol3 and/or Pol31 subunits. Using diagnostic PCNA mutants, we show that during DNA synthesis the carboxyl-terminal domain of Pol32 interacts with the carboxyl-terminal region of PCNA, whereas interactions of the other subunit(s) of Pol delta localize largely to a hydrophobic pocket at the interdomain connector loop region of PCNA.

Publication types

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

MeSH terms

  • Alleles
  • Binding Sites
  • DNA Polymerase I / chemistry
  • DNA Polymerase III / chemistry*
  • DNA Polymerase III / physiology
  • DNA Replication*
  • Phenotype
  • Proliferating Cell Nuclear Antigen / chemistry
  • Proliferating Cell Nuclear Antigen / metabolism*
  • Protein Subunits
  • Saccharomyces cerevisiae Proteins / chemistry*


  • Proliferating Cell Nuclear Antigen
  • Protein Subunits
  • Saccharomyces cerevisiae Proteins
  • DNA Polymerase I
  • DNA Polymerase III