Catalytic subunit of the DNA polymerase alpha complex (also known as the alpha DNA polymerase-primase complex) which plays an essential role in the initiation of DNA synthesis (PubMed:15314153, PubMed:15643072). During the S phase of the cell cycle, the DNA polymerase alpha complex (composed of a catalytic subunit pol1, an accessory subunit spb70/pol12 and two primase subunits, the catalytic subunit spp1/pri1 and the regulatory subunit spp2/pri2) is recruited to DNA at the replicative forks. The primase subunit of the polymerase alpha complex initiates DNA synthesis by oligomerising short RNA primers on both leading and lagging strands (By similarity). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Component of the alpha DNA polymerase complex (also known as the alpha DNA polymerase-primase complex) consisting of four subunits: the catalytic subunit pol1, the accessoryy subunit spb70/pol12, and the primase complex subunits spp1/pri1 and spp2/pri2 respectively (PubMed:11027257, PubMed:15314153). Interacts with mcl1 and mcm10 (PubMed:14766746, PubMed:15643072, PubMed:15915339). In eukaryotes there are five DNA polymerases: alpha, beta, gamma, delta, and epsilon which are responsible for different reactions of DNA synthesis. Belongs to the DNA polymerase type-B family.