The C-terminal domain of the DNA polymerase catalytic subunit regulates the primase and polymerase activities of the human DNA polymerase α-primase complex

J Biol Chem. 2014 Aug 8;289(32):22021-34. doi: 10.1074/jbc.M114.570333. Epub 2014 Jun 24.

Abstract

The initiation of DNA synthesis during replication of the human genome is accomplished primarily by the DNA polymerase α-primase complex, which makes the RNA-DNA primers accessible to processive DNA pols. The structural information needed to understand the mechanism of regulation of this complex biochemical reaction is incomplete. The presence of two enzymes in one complex poses the question of how these two enzymes cooperate during priming of DNA synthesis. Yeast two-hybrid and direct pulldown assays revealed that the N-terminal domain of the large subunit of primase (p58N) directly interacts with the C-terminal domain of the catalytic subunit of polα (p180C). We found that a complex of the C-terminal domain of the catalytic subunit of polα with the second subunit (p180C-p70) stimulated primase activity, whereas the whole catalytically active heterodimer of polα (p180ΔN-p70) inhibited RNA synthesis by primase. Conversely, the polα catalytic domain without the C-terminal part (p180ΔN-core) possessed a much higher propensity to extend the RNA primer than the two-subunit polα (p180ΔN-p70), suggesting that p180C and/or p70 are involved in the negative regulation of DNA pol activity. We conclude that the interaction between p180C, p70, and p58 regulates the proper primase and polymerase function. The composition of the template DNA is another important factor determining the activity of the complex. We have found that polα activity strongly depends on the sequence of the template and that homopyrimidine runs create a strong barrier for DNA synthesis by polα.

Keywords: C-terminal Domain; DNA Polymerase; DNA Polymerase Activity; DNA Polymerase α-Primase; DNA Primase; DNA Replication; DNA Replication Initiation; Primase Activity; Protein-Protein Interaction; RNA.

Publication types

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

MeSH terms

  • Catalytic Domain
  • DNA Polymerase I / chemistry*
  • DNA Polymerase I / genetics
  • DNA Polymerase I / metabolism*
  • DNA Primase / chemistry*
  • DNA Primase / genetics
  • DNA Primase / metabolism*
  • DNA Replication
  • Humans
  • Multienzyme Complexes / chemistry
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism
  • Protein Interaction Domains and Motifs
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Two-Hybrid System Techniques

Substances

  • Multienzyme Complexes
  • Protein Subunits
  • Recombinant Proteins
  • DNA Polymerase I
  • DNA Primase
  • DNA polymerase alpha-primase
  • DNA primase p58 subunit, human