Regulatory subunit of DNA primase, an RNA polymerase that catalyzes the synthesis of short RNA molecules used as primers for DNA polymerase during DNA replication. Stabilizes and modulates the activity of the small subunit, increasing the rate of DNA synthesis, and conferring RNA synthesis capability. The DNA polymerase activity may enable DNA primase to also catalyze primer extension after primer synthesis. May also play a role in DNA repair. Displays gap-filling and strand-displacement activities. Binds 1 [4Fe-4S] cluster. Heterodimer of a small subunit (PriS) and a large subunit (PriL). Belongs to the eukaryotic-type primase large subunit family. Truncated N-terminus.