ASCC3 review notes

Summary

Automated deep research status: just deep-research-falcon human ASCC3 --fallback perplexity-lite was run for this review. Falcon timed out after 600 seconds, and the configured perplexity-lite fallback failed with an API quota 401. No provider deep-research artifact was produced, so this review uses the cached UniProt, GOA, Reactome, and primary publication files plus the manual notes below.

ASCC3 is a large ATP-dependent SF2 helicase with two well-supported functional contexts. In the nucleus, it is the catalytic helicase subunit of the ASCC-ALKBH3 DNA dealkylation repair complex. Dango et al. show that ASCC3 unwinds DNA to provide the single-stranded substrate used by ALKBH3 for repair PMID:22055184. Brickner et al. further show alkylation-specific recruitment of ASCC3 to nuclear repair foci PMID:29144457.

In the cytosol, ASCC3 is the hRQT/RQT2 ATPase subunit of the ribosome quality control trigger complex. Hashimoto et al. define hRQT as ASCC3, ASCC2, and TRIP4 PMID:32099016, and Juszkiewicz et al. show that ASCC acts on ubiquitinated collided ribosomes to disassemble the lead ribosome PMID:32579943. Narita et al. refine this as K63-uS10-dependent hRQT-mediated subunit dissociation PMID:36302773.

PN projection

The PN workbook places ASCC3 under Translation > Cytosolic translation > Ribosome-associated QC > Ribosomal rescue with UniProt ID Q8N3C0 and synonym RQT2. The local projection report maps this path to two GO targets: GO:0072344 rescue of stalled cytosolic ribosome, which is already in GOA, and the broader GO:0006515 protein quality control for misfolded or incompletely synthesized proteins, listed as new to GOA.

Conservative decision: retain the exact ribosome-rescue/RQC annotations and do not add a new ASCC3 annotation to GO:0006515. ASCC3 has direct evidence for splitting K63-ubiquitinated collided ribosomes and thereby initiating RQC, but the existing GOA already captures this more specifically with GO:0072344, GO:0032790, and GO:1990116. The broad PN projection is biologically compatible as an ancestor/context term but would be redundant and less informative as a new gene-level assertion.

Annotation decisions

• Accept the DNA repair core: GO:0043138 3'-5' DNA helicase activity, GO:0006307 DNA alkylation repair, nuclear/nucleoplasm/nuclear-speckle locations, and GO:1990391 DNA repair complex.
• Accept the RQC core: GO:0180022 RQC-trigger complex, GO:0016887 ATP hydrolysis activity, GO:0022626 cytosolic ribosome, GO:0032790 ribosome disassembly, GO:0072344 rescue of stalled cytosolic ribosome, and GO:1990116 ribosome-associated ubiquitin-dependent protein catabolic process.
• Treat generic binding annotations conservatively. protein binding rows are interaction evidence but not informative molecular-function curation. Broad nucleic-acid/helicase terms should defer to the specific DNA helicase/ATPase/RQT annotations.
• Remove the DNA replication annotation: the cited ASCC1/ASCC damage-response paper supports alkylation repair-complex regulation, not a general DNA replication process for ASCC3.
• Remove the high-throughput membrane localization: ASCC3 is a soluble nuclear/cytosolic protein with no transmembrane-domain basis, and stronger curated evidence places it in ASCC/hRQT contexts.

Falcon deep research findings (2026-06-07)

A Falcon (Edison Scientific) deep-research report was generated (ASCC3-deep-research-falcon.md) and reviewed against the existing COMPLETE review. PMIDs below were resolved from the report's DOIs via the PubMed ID-converter and verified for exact titles; none of these five papers are cached in publications/, so they are added to references: as statement-only entries (full_text_unavailable: true, no supporting_text) and are NOT used to alter any annotation action.

• CONFIRMS (core MF/architecture): ASCC3 is a dual-cassette ("dual-engine") Ski2-like helicase whose two tandem NTPase/helicase cassettes are both catalytically active and can thread one substrate through both cassettes; TRIP4 docks via a Zn-finger and positions an ASCH domain next to the C-terminal cassette to stimulate the motor [PMID:37019967 Jia 2023 "ASCC3 can thread substrates through both helicase cassettes... TRIP4 docks on ASCC3 via a zinc finger domain"]. This reinforces the existing GO:0043138/GO:0016887 MF calls; no annotation change.
• NEW (partner-driven routing): TRIP4 and ALKBH3 bind ASCC3 mutually exclusively, providing a mechanism that routes the same helicase between the ALKBH3 alkylation-repair arm and TRIP4-associated functions [PMID:37019967 Jia 2023 "TRIP4 binds ASCC3 mutually exclusively with the DNA/RNA dealkylase, ALKBH3"]. Useful context for the two-arm model already captured; does not require a new GO term.
• NEW (translation initiation arm): The ASC-1 complex/ASCC3 also associates with scanning ribosomes and promotes translation initiation; ASCC3 localizes predominantly to 5' UTRs and its knockdown impairs 43S preinitiation-complex loading and scanning for a subset of transcripts [PMID:37092320 Kito 2023 "ASCC3... localizes predominantly to the 5' untranslated region... knockdown impairs 43S preinitiation complex loading and scanning dynamics"]. This is a distinct, non-RQC role; recorded as context and a suggested question rather than a new gene-level annotation (single study, mechanism still emerging).
• CONFIRMS/refines (RQC mechanism): In vitro reconstitution shows ribosomal collision is not strictly required for ZNF598 ubiquitination or ASCC-mediated disassembly; ASCC can split polysomes, monosomes, 80S elongation complexes, and even 48S initiation complexes once uS10 is K63-polyubiquitinated, provided >=30-35 nt of 3' mRNA downstream of the P site [PMID:38366554 Miscicka 2024 "ribosomal collision is not a strict prerequisite... as long as such complexes contained >= 30-35 3'-terminal mRNA nt downstream from the P site"]. Consistent with existing GO:0032790/GO:0072344 ribosome-rescue calls; refines mechanism, no action change.
• NEW (disease link): Biallelic loss-of-function ASCC3 variants cause an autosomal-recessive neurodevelopmental/neuromuscular syndrome (MIM:620700) with developmental delay, intellectual disability, hypotonia and motor/language impairment; three new Chinese families with compound-heterozygous variants reported [PMID:39286456 Li 2024 "neuromuscular syndrome caused by biallelic variants in ASCC3... compound heterozygous variants"]. Supports the biological importance of ASCC3 helicase function; added as reference + suggested question, no GO annotation change.
• PROVISIONAL (cancer/immune, single study, distinct pathway): In NSCLC, ASCC3 is reported upregulated and to stabilize STAT3 by recruiting CAND1 (inhibiting STAT3 ubiquitination), dampening the type I interferon response and fostering an immunosuppressive microenvironment [PMID:38148115 Ao 2023 "ASCC3 stabilized STAT3... by recruiting CAND1... impairing the type I interferon response"]. This is a single mechanism-of-disease study describing an indirect/regulatory role not clearly tied to the helicase core; recorded as reference and a suggested question only — deliberately NOT projected to any new MF/BP annotation.