DNA primase and DNA polymerase required to tolerate replication-stalling lesions by bypassing them (PubMed:26926109, PubMed:29073063). Required to facilitate mitochondrial and nuclear replication fork progression by initiating de novo DNA synthesis using dNTPs and acting as an error-prone DNA polymerase able to bypass certain DNA lesions (By similarity). Shows a high capacity to tolerate DNA damage lesions such as 8oxoG and abasic sites in DNA (By similarity). Provides different translesion synthesis alternatives when DNA replication is stalled: able to synthesize DNA primers downstream of lesions, such as ultraviolet (UV) lesions, R-loops and G-quadruplexes, to allow DNA replication to continue (By similarity). Can also realign primers ahead of 'unreadable lesions' such as abasic sites and 6-4 photoproduct (6-4 pyrimidine-pyrimidinone), thereby skipping the lesion (By similarity). Also able to incorporate nucleotides opposite DNA lesions such as 8oxoG, like a regular translesion synthesis DNA polymerase (By similarity). Also required for reinitiating stalled forks after UV damage during nuclear DNA replication (By similarity). Required for mitochondrial DNA (mtDNA) synthesis and replication, by reinitiating synthesis after UV damage or in the presence of chain-terminating nucleotides (PubMed:29073063). Prevents APOBEC family-mediated DNA mutagenesis by repriming downstream of abasic site to prohibit error-prone translesion synthesis (PubMed:26926109). Has non-overlapping function with POLH (By similarity). In addition to its role in DNA damage response, also required to maintain efficient nuclear and mitochondrial DNA replication in unperturbed cells (By similarity). Can act both with Mn(2+) and Mg(2+) as cofactor in vitro, but Mn(2+) is the preferred cofactor in vivo. The polymerase activity incorporates correct dNTPs with much higher efficiency with Mn(2+) than with Mg(2+). The fidelity is slightly more accurate when Mg(2+) is the cofactor compared to Mn(2+). In the presence of Mn(2+), a conformational transition step from non-productive to productive PRIMPOL:DNA complexes limits the enzymatic turnover, whereas in the presence of Mg(2+), the chemical step becomes rate limiting. Interacts with RPA1; leading to recruitment to chromatin and stimulate DNA primase activity. Interacts with SSBP1. Interacts with POLDIP2; leading to enhance DNA polymerase activity. Present in the nucleus, but a larger fraction is localized inside mitochondria. Associates with nuclear chromatin during the G1 and S phases of unperturbed cell cycles. Recruited to stalled replication forks following interaction with RPA1. The zinc knuckle motif binds zinc and is required for the DNA primase activity. It facilitates the binding and selection of the 5'-nucleotide of the newly synthesized primer and the recognition of preferred initiation sites. The RPA1-binding motifs (RBM) mediate interaction with RPA1 and are essential for recruitment to chromatin. The interaction is primarily mediated by RPA1-binding motif 1, which binds to the basic cleft of RPA1, with motif 2 plays a supporting role in RPA1-binding. The presence of an Asp-Aaa-Glu (DxE) motif in the metal-binding active site favors the use of Mn(2+) ions to achieve optimal incoming nucleotide stabilization, especially required during primer synthesis. Glu-116 is required to stabilize the incoming nucleotide at the 3'-site. Mice are viable but show defects in mitochondrial DNA synthesis. Belongs to the eukaryotic-type primase small subunit family.