CCNL2

CCNL2 (Cyclin L2) is a cell-cycle and RNA-processing regulator that operates as the activating cyclin for the kinase CDK11, where loss of the CCNL2/CDK11 locus on chromosome 1p36 sensitizes cancer cells to CDK11 inhibition and links CCNL2 to RNA splicing and homologous-recombination gene expression. Consistent with a role in cell-cycle control, CCNL2 protein physically associates with the lncRNA lnc-RNU12 in T cells, and depletion of this lncRNA alters CCNL2 levels and causes S-phase arrest (PMID:36165706). CCNL2 abundance is set by multiple converging regulatory inputs: its mRNA is bound and stabilized by the m5C reader YBX1 in cooperation with MATR3 (PMID:40707993), its transcription is activated by KLF3 (PMID:34937039), and its expression is post-transcriptionally suppressed by miR-214 (PMID:27381447). Through these inputs CCNL2 promotes cell proliferation and modulates chemoresistance, driving ovarian cancer proliferation and cisplatin resistance (PMID:40707993) and restraining smooth-muscle proliferation when downregulated by miR-214 (PMID:27381447). Beyond these regulatory and functional associations, direct biochemical reconstitution of the CCNL2 enzymatic role and its structural basis have not been characterized in the available corpus.

1. 2016 Medium

   Established that CCNL2 is a post-transcriptionally controlled regulator whose downregulation drives proliferation, answering whether CCNL2 levels have a defined cellular consequence.

   Evidence Luciferase reporter validation of miR-214 binding plus mimic/inhibitor rescue and proliferation/apoptosis assays in pulmonary artery smooth muscle cells

   PMID:27381447

   Open questions at the time

   • Does not identify the molecular effector through which CCNL2 limits proliferation
   • Restricted to a single cell type under hypoxia
2. 2021 Low

   Identified KLF3 as a transcriptional activator of CCNL2, addressing how CCNL2 expression is driven at the promoter level.

   Evidence GEO mining, luciferase/binding and rescue experiments along a miR-23a-3p → KLF3 → CCNL2 axis in a spinal cord ischemia/reperfusion model

   PMID:34937039

   Open questions at the time

   • Mechanistic detail of the KLF3–CCNL2 promoter interaction is limited
   • Single lab; direct KLF3 occupancy at the CCNL2 promoter not fully resolved
3. 2023 Medium

   Placed CCNL2 in a T-cell cycle-control circuit by showing it is a physical partner of a lncRNA whose loss arrests cells, answering whether CCNL2 protein engages RNA-based regulators.

   Evidence RIP showing lnc-RNU12 interaction with CCNL2 protein plus lncRNA knockdown with S-phase arrest in Jurkat T cells

   PMID:36165706

   Open questions at the time

   • Direct functional consequence of the CCNL2–lnc-RNU12 interaction (versus c-JUN co-binding) not separated
   • No reconstitution of the interaction
4. 2025 Medium

   Defined how CCNL2 mRNA stability is set, showing the m5C reader YBX1 with MATR3 stabilizes the transcript and that CCNL2 drives proliferation and chemoresistance.

   Evidence MeRIP m5C detection, YBX1 reader-residue mutagenesis, YBX1–MATR3 Co-IP and knockdown, with xenograft/PDX and cisplatin sensitivity assays in ovarian cancer

   PMID:40707993

   Open questions at the time

   • Single lab; m5C-site mapping on CCNL2 mRNA not detailed
   • Downstream effectors of CCNL2-driven cisplatin resistance unresolved
5. 2025 Low

   Assigned CCNL2 a molecular role as the activating cyclin for CDK11, connecting it mechanistically to RNA splicing and a therapeutic vulnerability.

   Evidence Integrative functional genomics, genetic and pharmacological CDK11 inhibition, and a genetically engineered mouse model with RNA splicing analysis (preprint)

   Open questions at the time

   • Preprint; direct biochemical reconstitution of a CCNL2–CDK11 complex not shown
   • Inference rests on co-deletion of CDK11 and CCNL2 at 1p36 rather than CCNL2-specific perturbation

• The catalytic/structural basis of CCNL2 as a CDK11 cyclin and the direct splicing substrates it controls remain undefined.
• No reconstituted CCNL2–CDK11 kinase complex
• No structural model
• Direct splicing targets dependent on CCNL2 not enumerated