Flexibility and distributive synthesis regulate RNA priming and handoff in human DNA polymerase α-primase

Abstract

In eukaryotes, DNA polymerase α-primase (pol-prim) initiates DNA synthesis during replication, generating the first ~30 nucleotides of nascent strands.1–5 Pol-prim is unique among replicative polymerases in its ability to perform de novo synthesis from a single-stranded DNA template; the primers it creates are required for further synthesis by the processive polymerases ε and δ that perform the bulk of nascent strand synthesis6,7. Pol-prim plays a particularly crucial role on the lagging strand during replication, as primers must be repeatedly synthesized due to the discontinuous nature of synthesis of this nascent strand.8 The primers generated by pol-prim are chimeric in nature, consisting of 7-10 ribonucleotides followed by ~20 deoxyribonucleotides.9,10 The RNA and DNA portions of this chimeric primer are generated by distinct active sites located in the primase and polymerase subunits of this tetrameric enzyme (Figure 1).11