CCNA1

CCNA1 (Cyclin A1) is a transcriptionally regulated cell-cycle gene whose expression is tightly controlled at the chromatin level and contributes to proliferative and stress-response programs in both germ cells and cancer (PMID:26250467, PMID:15215197). In germ cells, proximal sequences within −1.3 kb of the transcriptional start site are sufficient to drive spermatocyte-specific expression, with an upstream −4.8 to −1.3 kb region acting as an enhancer and conserved binding sites for A-myb, Hsf2, CDE, CHR, and CCAAT factors (PMID:15215197). In cancer, CCNA1 is a target of convergent epigenetic and transcriptional repression: in HPV-associated cervical cancer the HPV16 E7 oncoprotein forms a complex with DNMT1 at the CCNA1 promoter, depositing methylation marks that silence the gene through its CR3 domain (PMID:26250467), while in AML EZH2 deposits H3K27me3 on the promoter and the transcription factor FOXA2 directly represses transcription, loss of which raises CCNA1 and confers chemoresistance (PMID:34509612). CCNA1 is positively driven by RNF6, which binds the promoter and activates transcription to promote gastric cancer progression (PMID:37904524), and is post-transcriptionally silenced by miR-1271 targeting its 3′UTR, linking CCNA1 loss to AMPK activation and suppression of HBV-associated HCC (PMID:30565670). Beyond these regulatory inputs, the molecular substrates and direct biochemical activity of the CCNA1 protein itself have not been characterized in the available corpus.

1. 2004 Medium

   Established the cis-regulatory architecture driving CCNA1's restricted germ-cell expression, defining where and how the gene is transcriptionally controlled in spermatocytes.

   Evidence Transgenic mouse lacZ reporter assay with promoter deletion mapping and comparative sequence analysis

   PMID:15215197

   Open questions at the time

   • Does not identify which trans-acting factors occupy the conserved A-myb/Hsf2/CDE/CHR/CCAAT sites in vivo
   • Germ-cell regulation may differ from somatic/cancer contexts
2. 2015 Medium

   Showed that CCNA1 is an epigenetic silencing target of a viral oncoprotein, explaining its promoter hypermethylation in HPV-associated cancer.

   Evidence E7 knockdown/overexpression, ChIP, and methylation-specific PCR in cervical cancer cell lines

   PMID:26250467

   Open questions at the time

   • Functional consequence of CCNA1 silencing for tumor phenotype not dissected
   • Single lab, two cell lines
3. 2018 Medium

   Identified post-transcriptional control of CCNA1 by a microRNA, linking its downregulation to AMPK signaling and tumor suppression.

   Evidence Dual-luciferase 3′UTR reporter, miR-1271 mimic/inhibitor, and siCCNA1 rescue in HBV-HCC cells

   PMID:30565670

   Open questions at the time

   • Mechanism connecting CCNA1 loss to AMPK activation not resolved
   • Direct CCNA1 protein activity not addressed
4. 2021 Medium

   Demonstrated two orthogonal transcriptional repression mechanisms (EZH2/H3K27me3 and FOXA2) controlling CCNA1 and tied its derepression to chemoresistance in AML.

   Evidence ChIP, H3K27me3 promoter analysis, EZH2/FOXA2 manipulation, and drug sensitivity assays in AML cell lines

   PMID:34509612

   Open questions at the time

   • Whether EZH2 and FOXA2 act cooperatively or independently is unclear
   • No structural basis for FOXA2 promoter binding
5. 2023 Medium

   Placed CCNA1 downstream of an activating transcription factor, RNF6, establishing a positive regulatory input distinct from its repressive epigenetic controls.

   Evidence ChIP-seq, promoter binding, and CCNA1-silencing epistasis in gastric cancer cells

   PMID:37904524

   Open questions at the time

   • Direct binding versus indirect recruitment of RNF6 not fully separated
   • Effector function of CCNA1 in gastric cancer not defined
6. 2023 Low

   Linked a histone demethylase (KDM8) to CCNA1 regulation in oral squamous cell carcinoma, suggesting an additional chromatin-modifying input.

   Evidence Tissue microarray IHC, AITC pharmacological modulation, and xenograft models

   PMID:37893043

   Open questions at the time

   • Co-expression and drug response without direct demonstration of KDM8 acting at the CCNA1 locus
   • Single lab
7. 2024 Low

   Implicated CCNA1 as an upstream modulator of TGF-beta signaling in osteoblast differentiation, extending its role beyond cancer proliferation.

   Evidence siRNA knockdown, KEGG analysis, TGF-beta inhibitor rescue, and OVX mouse model

   PMID:38454404

   Open questions at the time

   • Pathway placement rests on inhibitor rescue without binding or direct epistasis
   • Mechanism connecting CCNA1 to TGF-beta unknown
8. 2026 Low

   Connected CCNA1 upregulation to radioresistance through ROS/antioxidant and AKT/mTOR-associated anti-apoptotic signaling in nasopharyngeal carcinoma.

   Evidence RNA-seq, CCNA1 knockdown, radiosensitivity/apoptosis assays, and ROS measurement in radioresistant cell lines

   PMID:41604083

   Open questions at the time

   • AKT/mTOR linkage inferred from phenotype without direct mechanistic dissection
   • Whether CCNA1 acts via canonical cyclin activity is untested

• The direct biochemical activity of the CCNA1 protein — its catalytic partners, substrates, and structural mechanism — remains uncharacterized in this corpus, which is dominated by transcriptional/epigenetic regulation of the gene rather than the protein's function.
• No CDK partner or substrate identified in the timeline
• No structural or enzymatic characterization
• Causal role downstream of regulatory inputs not biochemically defined