CLSPN

Claspin (CLSPN) functions in the DNA replication stress response, where it is required for activation of the checkpoint kinase CHK1: a coding variant that causes partial exon skipping and reduced Claspin expression correspondingly diminishes CHK1 activation (PMID:32847043). Beyond this checkpoint role, CLSPN expression is controlled post-transcriptionally through m6A regulation, whereby ALKBH5-mediated demethylation destabilizes CLSPN mRNA in an IGF2BP2-dependent manner, such that low ALKBH5 permits IGF2BP2-dependent stabilization of the transcript and drives docetaxel resistance in prostate cancer (PMID:41069850). In oral squamous cell carcinoma, CLSPN overexpression promotes glycolysis and proliferation through activation of Wnt/β-catenin signaling, with Wnt3a knockdown reversing these effects (PMID:38237848), although the biochemical link between Claspin and Wnt signaling is not resolved in the available corpus.

1. 2020 Medium

   Established that Claspin abundance is rate-limiting for CHK1 checkpoint activation by showing a splice-affecting coding variant reduces both Claspin expression and CHK1 phosphorylation.

   Evidence Minigene splicing assay and signaling/western blot experiments for the c.1574A>G (p.Asn525Ser) variant

   PMID:32847043

   Open questions at the time

   • Does not define the biochemical mechanism by which Claspin activates CHK1
   • Single study; effect of variant on patient phenotype not established
   • No structural characterization of the variant residue
2. 2020 Low

   Identified a promoter variant that elevates CLSPN transcription, indicating transcriptional regulation of Claspin levels.

   Evidence Luciferase reporter assay for the c.-68C>T promoter variant

   PMID:32847043

   Open questions at the time

   • Single method (luciferase) without functional follow-up
   • Transcription factor responsible not identified
   • No link to downstream CHK1 or phenotype
3. 2024 Medium

   Placed CLSPN upstream of Wnt/β-catenin signaling in cancer metabolism by showing its overexpression drives glycolysis and proliferation in a Wnt3a-dependent manner.

   Evidence Overexpression/knockdown, ECAR/OCR metabolic assays, xenografts, and Wnt3a-knockdown rescue in oral squamous cell carcinoma

   PMID:38237848

   Open questions at the time

   • Biochemical mechanism connecting Claspin to Wnt/β-catenin not resolved
   • Relationship to Claspin's canonical checkpoint role unclear
   • No direct physical partner in the Wnt pathway identified
4. 2025 Medium

   Defined post-transcriptional control of CLSPN through an m6A axis, explaining how its mRNA stability is tuned and links it to chemotherapy resistance.

   Evidence Multi-omics, knockdown/overexpression, organoid models, and clinical samples establishing the ALKBH5–IGF2BP2–CLSPN mRNA stability axis in prostate cancer

   PMID:41069850

   Open questions at the time

   • m6A site(s) on CLSPN mRNA not mapped
   • Single lab; mechanism of IGF2BP2-dependent stabilization not biochemically dissected
   • Connection between altered CLSPN levels and the checkpoint/Wnt functions not integrated

• The biochemical mechanism by which Claspin engages CHK1 and Wnt/β-catenin signaling, and how its post-transcriptional regulation integrates with these functions, remains unresolved.
• No structural or domain-level mechanism for CHK1 activation in the corpus
• Direct molecular link between Claspin and Wnt/β-catenin unknown
• No reported direct physical interactors of Claspin in the timeline