A novel function of CRL4(Cdt2): regulation of the subunit structure of DNA polymerase δ in response to DNA damage and during the S phase

J Biol Chem. 2013 Oct 11;288(41):29550-61. doi: 10.1074/jbc.M113.490466. Epub 2013 Aug 2.


DNA polymerase δ (Pol δ4) is a heterotetrameric enzyme, whose p12 subunit is degraded in response to DNA damage, leaving behind a trimer (Pol δ3) with altered enzymatic characteristics that participate in gap filling during DNA repair. We demonstrate that CRL4(Cdt2), a key regulator of cell cycle progression that targets replication licensing factors, also targets the p12 subunit of Pol δ4 in response to DNA damage and on entry into S phase. Evidence for the involvement of CRL4(Cdt2) included demonstration that p12 possesses a proliferating cell nuclear antigen-interacting protein-degron (PIP-degron) and that knockdown of the components of the CRL4(Cdt2) complex inhibited the degradation of p12 in response to DNA damage. Analysis of p12 levels in synchronized cell populations showed that p12 is partially degraded in S phase and that this is affected by knockdowns of CUL4A or CUL4B. Laser scanning cytometry of overexpressed wild type p12 and a mutant resistant to degradation showed that the reduction in p12 levels during S phase was prevented by mutation of p12. Thus, CRL4(Cdt2) also regulates the subunit composition of Pol δ during the cell cycle. These studies reveal a novel function of CRL4(Cdt2), i.e. the direct regulation of DNA polymerase δ, adding to its known functions in the regulation of the licensing of replication origins and expanding the scope of its overall control of DNA replication. The formation of Pol δ3 in S phase as a normal aspect of cell cycle progression leads to the novel implications that it is involved in DNA replication as well as DNA repair.

Keywords: Cell Cycle; DNA Damage Response; DNA Polymerase; DNA Repair; DNA Replication; Ubiquitin Ligase.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Binding Sites / genetics
  • Blotting, Western
  • Cell Line, Tumor
  • Cullin Proteins / genetics
  • Cullin Proteins / metabolism
  • DNA Damage*
  • DNA Polymerase III / chemistry
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism*
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Laser Scanning Cytometry
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Protein Structure, Tertiary
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • RNA Interference
  • S Phase*
  • Sequence Homology, Amino Acid
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • CUL4A protein, human
  • CUL4B protein, human
  • Cullin Proteins
  • DTL protein, human
  • Nuclear Proteins
  • Protein Subunits
  • Ubiquitin-Protein Ligases
  • POLD4 protein, human
  • DNA Polymerase III