AIGR Deep Research Report — mcm-4 (A0A061AL94, C. elegans)
Hypothesis under review (computational_prediction): ProtNLM2 predicts transcription initiation at RNA polymerase II promoter (GO:0006367) for A0A061AL94 (MCM-4). Is A0A061AL94 instead a minichromosome-maintenance (MCM2-7) replicative DNA helicase / replication-licensing factor, making the prediction a misassignment?
Executive Judgment
Verdict: REFUTED (prediction is a misassignment / over-annotation).
A0A061AL94 is unambiguously a fragment of the MCM2-7 replicative DNA helicase subunit MCM4, not an RNA polymerase II transcription-initiation factor. The evidence is decisive and computationally verifiable:
- A0A061AL94 is a 74-aa sequence (WormBase locus Y39G10AR.14b, gene mcm-4), submission-named by UniProt "DNA replication licensing factor mcm-4".
- Its only Pfam domain is PF21128 = "MCM4, winged helix domain" (WHD_MCM4) — an MCM4-specific signature.
- Its sequence is an exact substring (residues 750–823, the C-terminal 74 aa) of the reviewed Swiss-Prot entry MCM4_CAEEL (Q95XQ8, 823 aa). A0A061AL94 is therefore the isolated C-terminal winged-helix domain of full-length C. elegans MCM4.
- The reviewed parent entry (Q95XQ8) carries only DNA-replication GO terms (DNA helicase activity, ATP binding/hydrolysis, ssDNA binding, Zn binding, MCM complex, mitotic DNA replication initiation, premeiotic DNA replication, DNA strand elongation). No transcription-related GO term appears.
The most likely source of the ProtNLM2 error: the winged-helix (WHD) fold is a generic DNA-binding module shared by many bona-fide transcription factors, and a language model conflates "DNA replication initiation" with "transcription initiation" (frequency bias on the word "initiation"). GO:0006367 should not be applied to this gene product.
Caveat: A0A061AL94 is a 74-aa fragment, so it lacks the catalytic AAA+/Walker motifs (which lie in the parent's PF00493 domain upstream); the family assignment nonetheless rests on the MCM4-specific WHD signature and exact identity to the reviewed full-length MCM4.
Evidence Matrix
| Citation | Evidence type | Direction | Claim tested | Key finding | Context | Confidence / limitations |
|---|---|---|---|---|---|---|
| UniProt A0A061AL94 (database record) | Database / computational | Refutes prediction | Identity of A0A061AL94 | Gene mcm-4; submission name "DNA replication licensing factor mcm-4"; sole Pfam PF21128 = MCM4 winged-helix domain | C. elegans, WormBase Y39G10AR.14b | High; database-level, but corroborated below |
| InterPro/Pfam PF21128 (database) | Structural/evolutionary | Refutes | Domain identity of the 74-aa fragment | PF21128 = "MCM4, winged helix domain" — an MCM4-specific WHD | Family signature | High |
| UniProt Q95XQ8 MCM4_CAEEL (reviewed) + own sequence alignment | Structural/evolutionary (computed) | Refutes | Is A0A061AL94 part of MCM4? | 74-aa fragment is an exact match to residues 750–823 (C-terminus) of reviewed 823-aa MCM4_CAEEL; parent has PF00493 (MCM AAA+), PF17855, PF14551, PF17207, PF21128 | C. elegans | High; exact string identity computed in-run |
| UniProt Q95XQ8 curated GO set | Review/database | Refutes | Function of MCM4 | GO: DNA helicase activity (GO:0003678), ATP binding/hydrolysis, ssDNA binding, Zn binding, MCM complex, mitotic DNA replication initiation (GO:1902975), premeiotic DNA replication, DNA strand elongation; no transcription term | C. elegans | High |
| Yang et al. 2026, 41448435 | Review/mechanistic (human) | Qualifies (family biology) | MCM2-7 role | ORC/CDC6/CDT1 load MCM2-7 double hexamers to license replication origins — replication initiation, not transcription | Human, in vitro reconstitution | High for family; heterologous organism |
| Tomkins et al. 2025, 41365879 | Mechanistic (human) | Qualifies | MCM2-7 role | MCM2-7 helicase loaded onto origins in G1; geminin/CDT1 licensing control | Human | High for family |
| Yuan et al. 2017, 28191893 | Structural (cryo-EM, 3.9 Å) | Refutes | Function of MCM winged-helix domains | In the OCCM loading intermediate, flexible Mcm2-7 WHDs engage ORC-Cdc6; Mcm6 WHD binds Orc4 WHD — WHDs are replication-licensing structural elements | S. cerevisiae | High; the exact domain class of A0A061AL94 |
| Zhai et al. 2017, 28191894 | Structural (cryo-EM) | Refutes | Role of MCM C-terminal WHD | Mcm5 C-terminal WHD occludes the central channel of the Cdt1-Mcm2-7 helicase precursor (double-hexamer formation) | S. cerevisiae | High; helicase context, not transcription |
| Miller & Winston 2023, 36924499 | Genetic/genomic | Competing→resolved | Any MCM–transcription link | Related hit explicitly separates replication (MCM origin loading) from RNAPII transcription; no MCM transcription-initiation activity | S. cerevisiae | Rules out a moonlighting confound |
GO Curation Implications
- GO:0006367 (transcription initiation at RNA Pol II promoter, BP): REJECT / do not add. No experimental or reliable computational support; it conflicts with the well-established replicative-helicase identity. This is a paralog-independent misassignment driven by domain-fold ambiguity and word-frequency bias.
- Supported terms for mcm-4 (from reviewed parent Q95XQ8), as leads requiring curator verification:
- MF: DNA helicase activity (GO:0003678), ATP hydrolysis activity (GO:0016887), ATP binding (GO:0005524), single-stranded DNA binding (GO:0003697).
- BP: mitotic DNA replication initiation (GO:1902975), DNA strand elongation involved in DNA replication (GO:0006271), premeiotic DNA replication (GO:0006279).
- CC: MCM complex (GO:0042555), nucleus (GO:0005634), chromosome (GO:0005694).
- Because A0A061AL94 is only the C-terminal WHD fragment, MF catalytic terms describe the full protein/complex; for this isoform record, the WHD's role is regulatory/DNA-binding within the CMG helicase. "Protein binding" is not needed — more informative replication terms apply.
Mechanistic Scope
The immediate molecular function of MCM4 is as a subunit of the MCM2-7 hexameric ATPase, the catalytic core of the eukaryotic CMG (CDC45–MCM–GINS) replicative DNA helicase. Its processes are origin licensing and replication-fork unwinding during DNA replication initiation and elongation — a DNA-templated process at replication origins, mechanistically distinct from RNA polymerase II transcription initiation at promoters. The 74-aa C-terminal winged-helix domain contributes DNA binding/regulatory contacts within the helicase; it is not an RNA Pol II general transcription factor and is not part of the pre-initiation complex machinery (TFIIA/B/D/E/F/H, Mediator, Pol II).
Downstream mcm-4 loss-of-function phenotypes in the parent record (gonad development, premeiotic DNA replication, nervous-system development, locomotion) are secondary consequences of impaired replication, not evidence of a transcription-initiation activity.
Conflicts and Alternatives
- No credible conflicting evidence supports a transcription-initiation role. The prediction stands alone against domain, orthology, exact-sequence, and curated-GO evidence.
- Alternative explanation for the prediction (favored): WHD fold ambiguity (winged-helix domains occur in many transcription factors) + language-model frequency-bias conflation of "replication initiation" ↔ "transcription initiation." This is a classic ProtNLM naming artifact, not paralog confusion.
- Moonlighting confound checked and rejected (Iteration 2): A targeted search for an MCM/RNA-Pol-II transcription-initiation moonlighting activity returned no supporting primary evidence. The most relevant hit (36924499) explicitly separates MCM's replication role from RNAPII transcription. Cryo-EM structures (28191893 28191894) show the MCM WHD — the exact domain of A0A061AL94 — functions in origin licensing (engaging ORC-Cdc6), not at Pol II promoters.
- AlphaFold check (could-not-run): AlphaFold DB has no deposited model for A0A061AL94 or the reviewed parent Q95XQ8 (both HTTP 404), so a per-residue pLDDT/fold confirmation could not be executed; the WHD fold is instead established from the Pfam PF21128 signature and the cryo-EM literature above.
- Fragment caveat: the 74-aa isoform lacks Walker A/B and the MCM box (in the upstream AAA+ region), so catalytic MF terms should be curated on the full-length protein rather than asserted from this fragment alone.
Knowledge Gaps
- Isoform-specific function of Y39G10AR.14b (the 74-aa product). Checked: it maps exactly to the MCM4 C-terminus. Gap: whether this short isoform is independently expressed/functional. Matters because GO on isoform records should reflect the isoform. Resolution: WormBase expression/isoform annotation, RNA-seq isoform evidence.
- No PMID directly assaying C. elegans mcm-4 transcription activity (correctly — none is expected). Resolution: none needed; absence is consistent with refutation.
Discriminating Tests
- Domain/sequence (done): Pfam = MCM4 WHD; exact identity to reviewed MCM4 C-terminus → replication, not transcription. ✔
- Orthology: OrthoDB group 10251574at2759 clusters with eukaryotic MCM4 orthologs (replicative helicase), not with RNA Pol II GTFs.
- Complex membership / interactome: MCM4 co-purifies with MCM2/3/5/6/7 (MCM complex), CDC45, GINS — not with TFIID/Mediator/Pol II. A physical-interaction check would further discriminate.
- Structural: AlphaFold model of the 74-aa fragment should adopt a compact winged-helix fold consistent with MCM4 C-terminal WHD.
Curation Leads (require curator verification)
- Action: Do not annotate mcm-4/A0A061AL94 with GO:0006367; flag the ProtNLM2 prediction as a false positive (fold-ambiguity + "initiation" frequency bias).
- Replacement terms (leads): MF GO:0003678 (DNA helicase activity); BP GO:1902975 (mitotic DNA replication initiation); CC GO:0042555 (MCM complex) — transfer with appropriate evidence codes / IBA from the reviewed parent Q95XQ8.
- Candidate reference to verify (snippet): UniProt reviewed entry Q95XQ8 (MCM4_CAEEL) curated GO includes "mitotic DNA replication initiation" and "MCM complex," with no transcription term — supporting rejection of GO:0006367.
- Suggested question for curator: Should isoform record A0A061AL94 (74-aa WHD fragment) inherit full-length MCM4 MF/BP terms, or carry only CC/domain-appropriate annotation?
- Suggested experiment: Confirm MCM-complex co-fractionation / interactome membership of the mcm-4 gene product to formally exclude any Pol II association.
Paralog-Specificity Confirmation (Iteration 3)
To exclude MCM-paralog confusion, the 74-aa fragment was tested for exact-substring membership across the reviewed C. elegans MCM2-7 subunits. It is contained only in Q95XQ8 (MCM4, 823 aa) and is absent from the reviewed mcm-5 (Q21902, 759 aa) and mcm-6 (P34647, 810 aa) sequences. This confirms A0A061AL94 is specifically an MCM4 fragment, not a mis-mapped paralog. (UniProt gene-name search is fuzzy and returned some cross-hits by accession, but the substring test is unambiguous.)
Provenance
Computed in-run: UniProt REST fetch of A0A061AL94 (74 aa, gene mcm-4, Pfam PF21128 = MCM4 WHD) and Q95XQ8 (MCM4_CAEEL, 823 aa); exact-substring alignment placing the fragment at residues 750–823 (C-terminal WHD); enumeration of Q95XQ8 curated GO terms (all DNA-replication, none transcription); InterPro/Pfam lookup identifying PF21128 as "MCM4, winged helix domain."