CTC1 is a DNA-binding subunit of CST that presents the template and contacts polymerase alpha–primase. The existing annotations already cover ssDNA binding, telomeric DNA binding, CST membership, telomere maintenance and positive replication regulation. One compact core integrates these functions; no additional process assertion is needed merely because depletion disrupts an outcome.
Human CST structure maps a DNA anchor on CTC1, and contact-patch mutations impair DNA binding while leaving the heterotrimer assembled. The original structural paper distinguishes the STN1-bridged TEN1 association within one heterotrimer from contacts between neighboring complexes in a DNA-induced decamer. Neither observation establishes one obligatory native oligomer size. The source has an R978/R987 mutant-list discrepancy, which is not silently normalized. PMID:32499435, original Results, “ssDNA anchor patch”. The original main text is available in the selected cache; supplementary Methods were not recovered.
Modern experiments strengthen performed participation: CTC1 DNA-binding mutants retain polymerase association but impair template engagement and C-strand synthesis. Recruitment interfaces and an initiation-ready template scaffold are additional mechanistic evidence, while PRIM1 and POLA1 perform the catalytic reactions. Initiation stimulation does not demonstrate the topologically bound moving-polymerase mechanism required by GO:0030337. ROOT independently read the selected Methods/Results/Discussion of these four papers, and that scoped consultation is incorporated with attribution: PMID:35578024(https://doi.org/10.1038/s41594-022-00766-y), PMID:35831508(https://doi.org/10.1038/s41586-022-04930-8), PMID:35830881(https://doi.org/10.1038/s41586-022-05040-1), and PMID:38838667(https://doi.org/10.1016/j.cell.2024.05.002). Recombinant expression hosts, truncated POLA1, stabilization and model-assisted structures, engineered POT1/TPP1 and endogenous polymerase copurification limit the assays. Native human POT1 phosphorylation and a resolved ternary POT1–CST–polymerase structure are not established by the 2024 study.
CST overexpression also enhances recovery after hydroxyurea in HeLa cells. Three-subunit expression, rather than TEN1 or TEN1/STN1 alone, supports this effect; CTC1 expression was measured at mRNA level. The results support complex-level replication recovery and origin firing but do not independently establish all proposed dormant-origin mechanisms. PMID:25483097, selected original Methods/Results/Discussion. The older AAF donor paper is available here only as an abstract: it reports AAF-44/AAF-132 reconstitution and cofactor activity, with knockdown directed at AAF-44. Its complete original construct mapping was not recovered. PMID:19119139(https://doi.org/10.1074/jbc.M807593200).
The genuine 2012 Nature original and Online Methods were recovered separately from the protected abstract-only repository cache. Purified human CST, human-cell ChIP, depletion and fragment experiments support DNA binding and telomerase regulation. Its interaction work uses yeast two-hybrid and human-cell co-immunoprecipitation, and TPP1 residues 87–544 include mutations designed to disrupt TIN2 association. PMID:22763445(https://doi.org/10.1038/nature11269), “CST limits telomerase action”. Cache access flags are preserved; the review’s full-text availability assessment reflects actual external access.
Later pulse-chase and substrate-binding experiments distinguish inhibition of telomerase initiation from eviction of an elongating enzyme. DNA-anchor mutants and purification-salt controls help separate DNA engagement from polymerase copurification; high-concentration assemblies do not prove the same native oligomer state. PMID:34718732, selected original Methods/Results/Discussion. The broad negative-regulation annotation is retained without a universal eviction or exactly-one-extension-event claim.
The capping term GO:0016233 is not restricted to passive protection. The available 2012 source cites earlier protection, whereas its direct experiments establish binding and telomerase/length regulation. The 2009 human knockdown results and discussion leave replication versus end-protection contributions unresolved; severe Arabidopsis deprotection is a separate experimental context. The current capping assertion therefore remains UNDECIDED rather than being declared false. PMID:19854131(https://doi.org/10.1016/j.molcel.2009.09.017). The selected modern sources do not resolve a separable human end-protection step.
All three official VSP operations independently reconstruct Q2NKJ3-1 (1,217 residues) and Q2NKJ3-2 (1,031 residues). The shorter product deletes residues 217–251 and 1067–1217 and replaces 1053–1066. Its missing C-terminal region includes canonical DNA-contact residues K1164/K1167 and assembly architecture. The official premature-stop/NMD caveat is conditional; neither expression abundance nor equal function nor complete inactivity is established. Experimental fragments 1–701 and 844–1217 must not be renamed as the shorter official product.
The full interaction audit retains 69 complete 42-field records and 14 source-specific binding assertions. Nine matching current records ground five screen assertions, including three CTC1–APPBP2 yeast two-hybrid records and HEK293T/HCT116 AP-MS pairs with TEN1/STN1. Other original pairs are supported by primary reconstitution/structure or curator deference with explicit gaps. ROGID checks confirm backbone identity, not expression of an untagged canonical product or an exact experimental insert. The selected 2025 Methods were read, but its target supplementary table remained inaccessible; independent CST biology supports the pair without falsely claiming a table read. Its authentic publisher correction concerns a duplicated loss-function equation. PMID:40205054(https://doi.org/10.1038/s41586-025-08878-3); publisher correction.
Positive generic interactions remain KEEP_AS_NON_CORE under the project’s explicit standing instruction when no evidence-backed informative replacement is established. Partner activity is not transferred to CTC1. ACD/shelterin TPP1 (Q96AP0) is kept distinct from the unrelated O14773 protein also named TPP1 in official interaction metadata.
Five exact current IBDs at PTN001804660 match the five IBA terms. The human and mouse Ctc1 proteins occur in current PTHR14865 entries, with experimental human and mouse descendant grounding. Bounded tree/MSA retrievals failed, so no precise ancestral-path reconstruction, alignment identity, node-loss or divergence claim is made. Donor count and the target’s presence among experimental descendants are not objections. The biological annotations remain supported while propagation metadata explicitly records this unresolved access boundary.
The mouse Ctc1 donor Q5SUQ9 has the expected experimental terms. The separate Q8K2X3 ISS donor is mouse STN1: its own CST annotation is valid, but it is not the Ctc1 ortholog. The review retains positive human CST membership and the literal WITH/FROM while classifying this as a propagation/donor-method problem. The current GOA response also contains two date variants of the same CTC1–STN1 IPI assertion; both literal records are preserved behind the single seeded assertion.
HPA HPA052436 XML reports supported nucleoplasm and cytosol staining in A-549, HEK293 and U2OS. Only the existing nucleoplasmic assertion is assessed; no exclusive residence, product-specific localization or new cytosolic function is inferred. All five Reactome event graphs reach CTC1-containing CST in nucleoplasmic participants. This is location evidence and does not make CTC1 the RNA- or DNA-synthesizing enzyme.
Genuine isolated fetch and publication caching completed. The default Falcon attempt reached its bounded timeout and the configured fallback returned HTTP 401 quota failure. No provider file was fabricated or retried; these notes are manual synthesis. Existing main publication variants and global context are selected unchanged, with original normal-fetch variants retained separately for provenance. Portable source evidence records source hashes, access scopes, literal target records, products and source-specific decisions. The public record is manually compiled evidence, not a substitute primary publication.
Human CST overexpression increases new origin firing after hydroxyurea release. The DNA-fiber result is distinct from individual stalled-fork restart, which did not increase. EdU/PCNA labeling excludes altered entry into S phase as the explanation. The experiment overexpresses all three CST subunits; CTC1 abundance was estimated from mRNA. Polymerase recruitment or activation at dormant origins remains a proposed mechanism. This is the regulatory basis for the three retained GO:0045740 assertions; DNA-anchor mutants and the POLA1 interface separately establish CTC1 cofactor participation. PMID:25483097, Results and Methods; PMID:35578024(https://doi.org/10.1038/s41594-022-00766-y).
The single ssDNA-binding core now uses the existing, more specific telomere-lengthening process GO:0010833, the separately demonstrated negative telomerase regulation GO:0032211, and positive replication regulation GO:0045740. Telomeric-region localization complements the retained nuclear context for non-telomeric work. Typed is_a ancestry distinguishes the negative-regulation process from the process it regulates. No NEW annotation is added: the suggested GO:0032201 is below the existing telomere-maintenance assertion, and GO:0031297 fork processing is not established by increased origin firing without increased individual fork restart.
The Q8K2X3 ISS mapping is now REMOVE because its donor is mouse STN1, not the Ctc1 ortholog. This supersedes the earlier decision to retain that particular mapping. All literal source fields remain intact. Independent experimental CST membership and valid mouse Ctc1 transfers stay accepted, and the mouse STN1 source annotation itself remains sound.
The capping assertion remains UNDECIDED with explicit recognition of the PMID:19854130 abstract's Stn1-knockdown G-strand phenotype. This supports a complex-level protective context but does not settle CTC1-specific capping; unavailable full text may contain additional target experiments. The human PMID:19854131 data leave replication and end protection unresolved. This uncertainty does not impose a passive-only definition or deny mammalian protection. PMID:19854130(https://doi.org/10.1016/j.molcel.2009.08.009); PMID:19854131(https://doi.org/10.1016/j.molcel.2009.09.017).
The 2009 no-colocalization observation is retained as an assay-specific result. Its broader conventional-fork proposal cannot be used to exclude later non-telomeric regulation, but origin firing does not itself disprove that original observation or demonstrate direct action at conventional forks. Therefore no finding is marked contradicted or retracted. Short, source-exact anchors were added at load-bearing annotations and the regulatory core; aggregate source budgets include the unchanged earlier notes and quotes. Scientific access limits replace workflow narration in the review; detailed read provenance remains in the evidence index. The standalone description also includes CRMCC1/Coats plus from the unchanged official UniProt disease field (MIM:612199).