PRIM2

PRIM2 encodes the 58-kDa large subunit of the human DNA primase heterodimer (p49/p58), which synthesizes oligoribonucleotide primers required to initiate DNA replication and Okazaki fragment synthesis during lagging-strand replication (PMID:8530050). Consistent with this replicative role, PRIM2 expression is governed by the p53/RB/E2F axis—loss of p53 elevates PRIM2, E2F positively correlates with its expression, and PRIM2 depletion arrests the cell cycle, raises DNA damage, and drives senescence to curtail proliferation (PMID:35884433). Its abundance is further set translationally, as leucyl-tRNA synthetase (LARS) promotes leucine-dependent PRIM2 protein synthesis to activate DNA replication and cell cycle progression (PMID:41832550). Beyond replication, PRIM2 supports tumor cell survival and growth through additional routes: its loss depletes GSH and SLC7A11 and elevates lipid ROS, triggering ferroptosis (PMID:33149601), and it physically interacts with and stabilizes FAM111B to engage PI3K/AKT signaling and EMT (PMID:39556158).

1. 1995 High

   Established the core identity of PRIM2 by defining it as the p58 large subunit of the DNA primase heterodimer responsible for priming DNA synthesis.

   Evidence Chromosomal mapping and biochemical characterization of primase subunit composition

   PMID:8530050

   Open questions at the time

   • Does not resolve the catalytic vs. regulatory contribution of p58 within the heterodimer
   • No structural detail on primer length control or polymerase handoff from this entry
2. 2020 Medium

   Linked PRIM2 to redox/cell-death control, showing its loss induces ferroptosis rather than acting purely as a replicative housekeeping factor.

   Evidence siRNA knockdown in lung cancer cells with GSH, lipid ROS, MDA assays, SLC7A11/β-catenin Western blot, colony formation, and xenograft

   PMID:33149601

   Open questions at the time

   • Mechanism connecting primase subunit loss to SLC7A11 downregulation is not defined
   • Single lab; whether ferroptosis is secondary to replication stress is unresolved
3. 2022 Medium

   Placed PRIM2 within the p53/RB/E2F regulatory circuit and tied its depletion to cell cycle arrest, DNA damage, and senescence, explaining its proliferative role.

   Evidence siRNA knockdown with cell cycle/DNA damage/senescence assays plus p53 mutation/deletion analysis and E2F correlation in lung cancer cells

   PMID:35884433

   Open questions at the time

   • Direct E2F binding to the PRIM2 promoter not demonstrated
   • Single lab; causal hierarchy between DNA damage and senescence not separated
4. 2024 Medium

   Identified a physical PRIM2 partner (FAM111B), revealing a signaling function beyond replication via PI3K/AKT and EMT.

   Evidence Co-immunoprecipitation, protein stability and RT-qPCR assays, proliferation/migration assays, and xenograft in pancreatic ductal adenocarcinoma

   PMID:39556158

   Open questions at the time

   • Single Co-IP without reciprocal/structural validation of the interaction interface
   • How PRIM2 stabilizes FAM111B mechanistically is unknown
5. 2026 Medium

   Demonstrated translational control of PRIM2 by LARS, showing nutrient (leucine) availability gates PRIM2 synthesis and downstream DNA replication.

   Evidence SILAC measurement of leucine-dependent PRIM2 synthesis, transcriptome/proteome profiling, LARS/PRIM2 perturbation, and functional assays in osteosarcoma

   PMID:41832550

   Open questions at the time

   • Molecular intermediary linking LARS leucine sensing to PRIM2 mRNA translation not identified
   • Single lab; generality across tissues untested

• How the canonical primase activity of PRIM2 mechanistically connects to its reported roles in ferroptosis suppression and PI3K/AKT-EMT signaling remains unresolved.
• No structural model of PRIM2 in any human study within the corpus
• Whether non-replicative phenotypes are direct or secondary to replication stress is unknown