CG8915 encodes a 976-residue DEAH-box (DHX-type) RNA helicase. It has an N-terminal R3H domain, a two-lobed helicase core with an intact ATP-binding P-loop (GATGSGKST) and a DEAH motif II, and C-terminal HA2 and OB-fold domains. PANTHER places it in the YTHDC2 subfamily of DEAH helicases, and its best bidirectional human match is YTHDC2. Unlike vertebrate YTHDC2, CG8915 has no ankyrin-repeat insertion between its helicase lobes and no YTH N6-methyladenosine-reader domain. It is also distinct from the fly YTHDC2-family paralog Bgcn, whose helicase motifs are degenerate. By conserved mechanism, CG8915 is expected to act as an RNA-stimulated ATPase that unwinds or remodels RNA with 3'-to-5' polarity. Its RNA targets, partners, subcellular location and biological role have not been studied experimentally. The transcript is maternally deposited and is detected in embryonic primordial germ cells.
Summary: Correct but general; the conserved Walker A P-loop specifies ATP as the bound nucleotide.
Reason: CG8915 retains the canonical motif I P-loop (GATGSGKST) of DEAH/RHA helicases, which binds ATP. The specific term ATP binding (GO:0005524) is already on the gene from a separate IEA row and is the appropriate refinement.
Summary: Correct but general; the R3H domain and DEAH/RHA helicase core indicate RNA as the substrate.
Reason: R3H domains are single-stranded nucleic acid binding modules found in RNA-processing proteins, and DEAH/RHA helicases with HA2 and OB-fold domains act on RNA. The RNA binding term (GO:0003723) is already on the gene by IBA and is the appropriate refinement. No DNA-directed activity has been suggested for this branch.
Summary: RNA binding is inherited from the deep PTHR18934 DEAH-helicase ancestor and is consistent with CG8915's intact R3H and helicase core.
Reason: PAINT placed RNA binding at PTN008360424, a broad ancestral node of the DEAH/RHA helicase family. CG8915 descends from it and has no feature arguing against inheritance. It keeps the R3H domain and an intact helicase core with HA2 and OB-fold domains. RNA binding is an intrinsic requirement of DEAH helicase activity, so this is a core function even though the specific RNA targets are unknown.
Propagation Review
Root cause:NO FAILURE CORE
Sources checked:
PANTHER:PTN008360424SUPPORTS TRANSFER
Broad DEAH-family ancestor. CG8915 retains the RNA-binding helicase architecture, so the inherited assertion holds.
Summary: The inherited helicase activity is sound. CG8915 is an intact DEAH/RHA RNA helicase, so 3'-5' RNA helicase activity is the appropriate refinement.
Reason: The PAINT node supports generic helicase activity. Within PTHR18934, Bgcn's NOT helicase assertion is confined to its own IRD node (PTN000433935), which does not cover CG8915. CG8915 itself keeps the catalytic motifs that Bgcn lost. The gene already carries GO:0034458 3'-5' RNA helicase activity (FlyBase ISS from human YTHDC2, its subfamily neighbour in PTHR18934:SF213). That term is a descendant of helicase activity, so this row is refined to it rather than kept as a separate broad claim.
Propagation Review
Root cause:TERM SCOPING PROBLEM
Failure modes:GRANULARITY MISMATCH
Sources checked:
PANTHER:PTN008360424SUPPORTS TRANSFER
The transfer is correct but generic. The more specific 3'-5' RNA helicase term is supported by the target's own conserved motifs and by the ISS from YTHDC2.
Summary: CG8915 retains the canonical Walker A (motif I) ATP-binding P-loop of DEAH helicases.
Reason: The aligned motif I in CG8915 (232-240 GATGSGKST) matches the GxTGSGKT/ST consensus that binds ATP in DEAH/RHA helicases. This contrasts with Bgcn, whose motif I is degenerate (AALCWDKSV) and is reported to preclude ATP binding. ATP binding is intrinsic to the helicase core function.
Summary: Correct but uninformative; the relevant hydrolase activity is the RNA-stimulated ATP hydrolysis that powers the helicase.
Reason: An earlier version of this review refined this row to 3'-5' RNA helicase activity. In current GO, helicase activity sits under ATP-dependent activity and isomerase activity, not under hydrolase activity, so that term is not a refinement of this row. The hydrolase activity that CG8915 can be inferred to have is ATP hydrolysis. It retains the DEAH motif II (Walker B) residues needed for ATP hydrolysis, and DEAH helicases such as YTHDC2 are RNA-induced ATPases. GO:0016887 ATP hydrolysis activity is a descendant of hydrolase activity and expresses this claim.
Summary: A sound curator transfer from human YTHDC2, a member of the same PANTHER subfamily (SF213), to a protein that keeps the complete catalytic helicase core.
Reason: The transfer is limited to the helicase core, which CG8915 shares with YTHDC2 (about 43-44% identity over both helicase lobes). Human YTHDC2 is biochemically an RNA-induced ATPase with 3'-to-5' helicase activity, and 3'-to-5' translocation is the general polarity of DEAH/RHA helicases. CG8915 lacks the YTHDC2 ankyrin-repeat insertion and the YTH domain, so no N6-methyladenosine recognition or ARD-dependent partner recruitment is implied by this row. The FlyBase ISS is accepted as the core molecular function, with the caveat that no Drosophila enzymology exists.
CG8915 therefore has the R3H plus intact DEAH helicase architecture without the two YTHDC2-specific accessory modules.
file:DROME/CG8915/CG8915-uniprot.txt
DR PANTHER; PTHR18934:SF213; 3'-5' RNA HELICASE YTHDC2; 1.
Core Functions
ATP-dependent DEAH-box RNA helicase that binds RNA through its R3H and helicase core and unwinds or remodels it with 3'-to-5' polarity. The function is inferred from the intact catalytic motifs and from YTHDC2 subfamily membership. The RNA substrates and biological context are unknown.
Q: Should PAINT add a 3'-5' RNA helicase activity IBD at the PTHR18934:SF213 YTHDC2-subfamily node, or should CG8915 continue receiving only broad helicase activity by IBA until the Drosophila YTHDC2/Bgcn phylogeny and Drosophila-specific helicase polarity are resolved?
Q: Is CG8915 the Drosophila ortholog of the YTH-less, R3H-intact YTHDC2-like paralog found in other schizophoran flies, which has since lost the ankyrin-repeat insertion? Or is it a separate R3H-DEAH lineage within PTHR18934:SF213? A tree of SF213 sequences that includes CG8915, Bgcn and the non-Drosophila schizophoran copies would settle this.
Suggested Experiments
Experiment: Test recombinant CG8915 for RNA-stimulated ATPase activity and for unwinding of 3'-tailed versus 5'-tailed RNA duplexes, with a motif II (DEAH to AAAH) mutant as the negative control.
Type: in vitro biochemistry
Experiment: Identify CG8915-bound RNAs and protein partners in ovary or early embryo (for example by CLIP and IP-mass spectrometry of an endogenously tagged allele), and test whether CG8915 associates with Bam, Bgcn or other germline RNA regulators.
Type: RNA-protein interaction profiling
External Prediction Reviews
These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.
LSP — Less precise than existing annotation Review score: 2/2
Prediction method: ProtNLM2 · Version: UniProt API snapshot 2026-09-08
Review rationale: Nucleic acid binding is supported by the R3H domain and conserved RNA-helicase architecture. RNA binding is the existing, more specific assignment. Target sequence analysis retains the ATP-binding and DEAH motifs, although the broad RNA-binding conclusion does not depend on resolving every aspect of catalysis or YTHDC2-family phylogeny.
Supporting Evidence:
file:DROME/CG8915/CG8915-bioinformatics/RESULTS.md: "CG8915/Q9VX63 retains a canonical ATP-binding P-loop and DEAH catalytic motif. It differs from the inactive helicase-like protein Bgcn/Q9W1I2 at both diagnostic regions."