Protein phosphatase-1 is targeted to DNA polymerase delta via an interaction with the p68 subunit

Biochemistry. 2008 Oct 28;47(43):11367-76. doi: 10.1021/bi801122t. Epub 2008 Oct 1.


Protein phosphatase-1 (PP1) is a Ser/Thr protein phosphatase that participates in the phosphorylation/dephosphorylation regulation of a diverse range of cellular processes. The PP1 catalytic subunit (PP1) achieves this by its ability to interact with many targeting subunits such that PP1 activity is thereby specified against phosphoprotein substrates in the microvicinity of its targeting subunit. DNA polymerase delta (Pol delta) is a key enzyme in mammalian chromosomal replication. It consists of four subunits, p125, p50, p68, and p12. We identify p68 as a novel PP1 targeting subunit. PP1 was shown to associate with human DNA polymerase delta by affinity chromatography and coimmunoprecipitation assays from mammalian cell lysates and in vitro by pull-down assays. The binding domain for PP1 was identified as the sequence KRVAL, a variant of the canonical RVxF PP1 binding motif. These studies provide the first evidence for the targeting of PP1 to DNA polymerase delta. We also show that CK2 phosphorylates the Pol delta p125, p68, and p12 subunits and that these phosphorylated subunits are substrates for PP1. These findings identify a new role for p68 as a PP1 targeting subunit that implicates PP1 in the dephosphorylation of Pol delta. Our findings also show that CK2 is a strong candidate for the protein kinase involved in the in vivo phosphorylation of p68.

Publication types

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

MeSH terms

  • Binding Sites / genetics
  • Catalytic Domain / genetics
  • DEAD-box RNA Helicases / chemistry*
  • DEAD-box RNA Helicases / genetics
  • DNA Polymerase III / chemistry
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism*
  • HeLa Cells
  • Humans
  • Models, Biological
  • Protein Binding / genetics
  • Protein Phosphatase 1 / chemistry
  • Protein Phosphatase 1 / genetics
  • Protein Phosphatase 1 / metabolism*
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism


  • Protein Subunits
  • Recombinant Proteins
  • DNA Polymerase III
  • Protein Phosphatase 1
  • Ddx5 protein, human
  • DEAD-box RNA Helicases