CCND3

CCND3 (Cyclin D3) is a D-type cyclin that drives G1/S cell cycle progression by partnering with CDK4 (and CDK6) to phosphorylate the Rb tumor suppressor, and its expression is gated by mitogenic and hormonal cues — glucocorticoids suppress both CCND3 and CDK4 to lower Rb phosphorylation and enforce G0 arrest, while CCND3 overexpression restores Rb-kinase activity and confers apoptosis resistance (PMID:7664296). Its abundance is set at multiple regulatory tiers: transcriptionally by FOXO1 in B-ALL (PMID:35013097), translationally through PTBP1 binding to its 5'-UTR (PMID:31301177) and METTL5-mediated 18S rRNA m6A modification that boosts translation efficiency (PMID:41743013), and through numerous miRNAs that directly target its transcript (miR-592, miR-212, miR-4779, miR-15b) to drive cell-cycle arrest and apoptosis upon CCND3 loss (PMID:26144250, PMID:26064240, PMID:27493231, PMID:29362401). Beyond the kinase complex, CCND3 has a CDK4/6-independent pro-survival role that includes promoting CDK8 transcription, such that its elevation drives palbociclib resistance (PMID:35013097), and it limits epithelial-mesenchymal transition by facilitating PARK2-mediated ubiquitination and degradation of vimentin, with its loss promoting metastasis and chemoresistance (PMID:39781469). CCND3 also acts as an interferon-stimulated gene with a non-nuclear antiviral function: upon bandavirus infection it translocates to the cytoplasm and, via its CN domain, binds the viral nucleoprotein to block RNP assembly (PMID:40858603). CCND3 is recurrently dysregulated in cancer through a KCNMB4-CCND3 fusion in osteosarcoma (PMID:25300797) and through aberrant stabilization by upstream regulators such as PRAME (PMID:39071619).

1. 1995 High

   Established CCND3's canonical engine role — that it partners with CDK4 to phosphorylate Rb and that this activity is the target of glucocorticoid-mediated growth arrest, linking the cyclin directly to cell-cycle exit and apoptosis control.

   Evidence Stable overexpression, Rb-1 kinase activity assay, SV40 T antigen rescue, and serum-free apoptosis assay in lymphoid cells

   PMID:7664296

   Open questions at the time

   • Did not resolve CDK4/6-independent functions
   • Mechanism of glucocorticoid-driven transcriptional suppression of CCND3 not defined here
2. 2015 Medium

   Identified direct miRNA control of CCND3 — multiple miRNAs target its transcript to enforce cell-cycle arrest and apoptosis, defining post-transcriptional brakes on cyclin abundance across tumor and immune contexts.

   Evidence Dual-luciferase reporter assays, miRNA mimic/inhibitor transfection, knockdown phenotyping, and in vivo models for miR-592 (colorectal), miR-15b (B cells/lupus), later extended to miR-212 (ATL) and miR-4779 (colon)

   PMID:26064240 PMID:26144250 PMID:27493231 PMID:29362401

   Open questions at the time

   • Relative contribution of each miRNA in physiological settings unclear
   • No integrated model of combinatorial miRNA regulation
3. 2019 High

   Revealed translational control of CCND3, showing PTBP1 binds the 5'-UTR to enhance translation and is itself a miRNA target, layering a translational tier onto cyclin regulation.

   Evidence RBP co-IP, 5'-UTR reporter assay, and miR-194 target validation in hepatocellular carcinoma

   PMID:31301177

   Open questions at the time

   • Whether PTBP1 control of CCND3 operates outside HCC not established
   • Structural basis of 5'-UTR recognition undefined
4. 2022 Medium

   Separated CCND3's pro-survival function from its kinase-complex role, showing it is essential for B-ALL survival independent of CDK4/6 activity and drives CDK4/6-inhibitor resistance.

   Evidence CCND3 knockdown vs. palbociclib comparison, FOXO1 perturbation, and gene expression analysis in B-ALL

   PMID:35013097

   Open questions at the time

   • Molecular basis of the CDK4/6-independent anti-apoptotic activity beyond CDK8 transcription unresolved
   • Single lineage (B-ALL) tested
5. 2024 Medium

   Defined an upstream stabilization pathway in which PRAME elevates CCND3 by degrading negative regulators (CTMP, p21) to activate Akt signaling, connecting CCND3 accumulation to oncogenic proliferation in myeloma.

   Evidence PRAME knockdown/overexpression, co-IP, ubiquitination assays, and proliferation readouts in multiple myeloma cells

   PMID:39071619

   Open questions at the time

   • No in vitro reconstitution of the Cul2 ligase activity
   • Direct measurement of CCND3 stability changes not shown
6. 2025 Medium

   Uncovered a CDK-independent cytoskeletal role: CCND3 facilitates PARK2-mediated vimentin ubiquitination, so its transcriptional loss via PI3K/Akt/c-Jun triggers EMT, metastasis, and cisplatin resistance.

   Evidence CCND3 knockdown, PARK2-vimentin ubiquitination assays, pathway inhibitors, migration/invasion assays, and clinical correlation in lung adenocarcinoma

   PMID:39781469

   Open questions at the time

   • How CCND3 facilitates PARK2 recruitment to vimentin mechanistically unknown
   • Whether this is direct or via intermediary not resolved
7. 2025 High

   Demonstrated a non-nuclear antiviral function, establishing CCND3 as an interferon-stimulated gene that translocates to the cytoplasm and uses its CN domain to bind bandavirus nucleoprotein and block RNP assembly.

   Evidence ISG screening, subcellular fractionation/imaging, co-IP with domain mapping, RNA-independent binding assay, interface mapping, and in vivo infection model

   PMID:40858603

   Open questions at the time

   • Breadth of antiviral activity beyond bandaviruses unknown
   • Whether antiviral and cell-cycle functions are mutually exclusive states unclear
8. 2026 Medium

   Added a ribosome-level translational control mechanism: METTL5-deposited 18S rRNA m6A enhances CCND3 translation efficiency, coupling rRNA modification to cyclin output and tumorigenesis.

   Evidence METTL5 knockout, RNC-seq for translation efficiency, western blot, and in vivo/in vitro assays in oral squamous cell carcinoma

   PMID:41743013

   Open questions at the time

   • Selectivity of METTL5 for CCND3 vs. global translation effects not isolated
   • Single tumor type tested
9. 2025 Medium

   Detailed post-translational stabilization via p21, where CDKN1A binding occludes Thr283 phosphorylation to block CCND3 nuclear export and proteasomal degradation, extending its nuclear half-life.

   Evidence Reciprocal co-IP, phosphorylation site analysis, half-life assay, and AlphaFold2/molecular dynamics modeling in butyrate-treated intestinal cells (preprint)

   PMID:bio_10.1101_2025.06.19.660543

   Open questions at the time

   • Preprint, not yet peer-reviewed
   • Structural prediction of Thr283 burial awaits experimental validation
10. 2025 Low

    Linked C-terminal truncating variants to oncogenic gain-of-function, inferring that loss of degradation signals increases CCND3 stability in pediatric cancers.

    Evidence COSMIC somatic mutation pattern analysis and pediatric genomics cohort interrogation (preprint)

    PMID:bio_10.1101_2025.11.20.25340490

    Open questions at the time

    • No direct biochemical reconstitution of protein stability
    • Inference from mutation pattern only; preprint

• How CCND3's distinct activities — Rb-directed kinase function, CDK4/6-independent survival signaling, cytoskeletal/EMT control, and cytoplasmic antiviral defense — are coordinated and switched within a single cell remains unresolved.
• No unified model integrating nuclear and cytoplasmic functions
• Structural basis of CDK4/6-independent functions undefined
• Physiological triggers governing function-switching unknown