Non-catalytic component of DNA polymerase alpha, which in a complex with DNA primase (DNA polymerase alpha:primase) constitutes a replicative polymerase. POL12 may play an essential role at the early stage of chromosomal DNA replication by coupling DNA polymerase alpha to the cellular replication machinery (By similarity). Interacts with MCM10. DNA polymerase alpha:primase is a four subunit enzyme complex, which is assembled throughout the cell cycle, and consists of the two DNA polymerase subunits A POL1 and B POL12, and the DNA primase large PRI2 and small PRI1 subunits (PubMed:3061469). Subunit B POL12 binds to subunit A POL1 (PubMed:19494830). Phosphorylated in a cell cycle-dependent manner. Present with 11200 molecules/cell in log phase SD medium. Belongs to the DNA polymerase alpha subunit B family.