DCAF12L2 is an intronless retrocopy of DCAF12 (chromosome 9) located on the X chromosome (Xq25). It encodes a 463-amino-acid WD40 beta-propeller protein belonging to the DCAF12 family. By phylogenetic inference, it is predicted to be a component of the Cul4-RING E3 ubiquitin ligase complex, where it would serve as a substrate receptor via its WD40 domain. Peer-reviewed mechanistic characterization is restricted to the parent gene DCAF12; for DCAF12L2 itself, the most direct functional claims (CRL4^DCAF12L2 recognizing MEKK4 and the WDR11/FAM91A1 complex, plus cancer-associated WD40 mutations P334L/R335C/R335H disrupting substrate binding) come from a thesis-level source (Onireti 2022) and have not been independently validated. Conversely, a 2025 thesis (Kolรกลovรก, *"CRL4DCAF12 ubiquitin ligase: a novel factor in DNA replication control"*) reports no detectable DDB1 binding and no MCMBP binding for DCAF12L2 โ also at thesis-level evidence tier โ leaving it unclear whether DCAF12L2 assembles a fully functional CRL4 complex. It is classified as Tdark in Pharos. Expression is enriched in testis (late spermatids) and epididymis, consistent with X-linked retrocopies co-opted for spermatogenesis. The parent gene DCAF12 recognizes C-terminal diglutamate degrons on substrates including MAGEA3, MAGEA6, CCT5, and MOV10 via the DesCEND pathway, but whether DCAF12L2 shares this substrate specificity remains unproven.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0080008 Cul4-RING E3 ubiquitin ligase complex | IBA GO_REF:0000033 | ACCEPT | Summary: This annotation is inferred by phylogenetic analysis (IBA) from the Drosophila ortholog DCAF12 (FBgn0037980) and human paralog DCAF12 (Q5T6F0), both of which are experimentally confirmed components of CRL4 complexes. DCAF12L2 belongs to the DCAF12 family and contains the WD40 beta-propeller architecture characteristic of CRL4 substrate receptors. While no direct experimental evidence confirms DCAF12L2 in a CRL4 complex, the phylogenetic inference is reasonable given the conserved domain architecture. Reason: The IBA annotation is well-supported by the conserved WD40 beta-propeller domain architecture and family membership. The parent gene DCAF12 is a confirmed CRL4 substrate receptor with cryo-EM structural data showing the DDB1-DCAF12-substrate complex. The Drosophila ortholog likewise functions in CUL4-DDB1 complexes. Although DCAF12L2 itself lacks direct experimental confirmation, the phylogenetic inference is the strongest available evidence for a Tdark protein and correctly reflects the most likely complex membership. Supporting Evidence: GO_REF:0000033 [IBA annotation transferred from Drosophila DCAF12 (FBgn0037980) and human DCAF12 (Q5T6F0) via PANTHER phylogenetic tree PTN002323498] file:human/DCAF12L2/DCAF12L2-deep-research-bioreason-sft.md [BioReason correctly identifies DCAF12L2 as belonging to the DCAF12 family with WD40 beta-propeller architecture consistent with CRL4 substrate receptor function] file:human/DCAF12L2/DCAF12L2-deep-research-falcon.md Human **DCAF12L2** (DDB1- and CUL4-associated factor 12-like protein 2; also called **WDR40C**) is a WD40-repeat protein proposed to act as a **substrate receptor (DCAF)** for **CUL4โDDB1 (CRL4)** cullin-RING E3 ubiquitin ligases, thereby providing substrate specificity for ubiquitin-dependent proteasomal degradation. file:human/DCAF12L2/DCAF12L2-deep-research-falcon.md A separate experimental source (2025) tested DCAF12L2 (and DCAF12L1) for interaction with **MCMBP** (a known DCAF12 substrate in that research program) and found **no detectable binding**, consistent with prior work that neither DCAF12L1 nor DCAF12L2 binds the same **C-terminal acidic end** degron as DCAF12. The authors also report **no significant binding of DDB1** to DCAF12L1 or DCAF12L2 in their assays, concluding it remains unclear whether these paralogs can assemble a fully functional CRL4 complex under those conditions. |
| GO:1990756 ubiquitin-like ligase-substrate adaptor activity | IBA GO_REF:0000033 | NEW | Summary: DCAF12L2 is predicted to function as a ubiquitin ligase substrate adaptor based on its membership in the DCAF12 family. The parent gene DCAF12 is a confirmed substrate receptor for the CRL4-DDB1 E3 ubiquitin ligase, recognizing C-terminal diglutamate degrons on MAGEA3, MAGEA6, CCT5, and MOV10. While no direct evidence exists for DCAF12L2 adaptor activity, the conserved WD40 domain architecture supports this inference. Reason: This is the predicted molecular function based on phylogenetic and domain architecture evidence. The parent gene DCAF12 serves as substrate adaptor via its WD40 beta-propeller; DCAF12L2 retains this domain, supporting a similar molecular function. Note for curators: this annotation is NOT currently in the GOA for DCAF12L2; action: NEW means we are recommending it be added based on the core-function analysis below. The evidence_type: IBA and original_reference_id: GO_REF:0000033 values describe the inference style/source we are proposing. Supporting Evidence: PMID:38665159 ...Damaged DNA-binding protein-1 (DDB1)- and CUL4-associated factor 12 (DCAF12) serves as the substrate recognition component within the Cullin4-RING E3 ligase (CRL4) complex, capable of identifying C-terminal double-glutamic acid degrons to promote the degradation of specific substrates through the ubiquitin proteasome system... PMID:16949367 ...we identify 18 Ddb1- and Cul4-associated factors (DCAFs), including 14 containing WD40 repeats. DCAFs interact with multiple surfaces on Ddb1, and the interaction of WD40-containing DCAFs with Ddb1 requires a conserved "WDXR" motif... file:human/DCAF12L2/DCAF12L2-deep-research-falcon.md High-confidence structural/biochemical work on human **DCAF12** shows it behaves as a **canonical WD40 DCAF substrate receptor**: it binds substrates carrying a **C-terminal double glutamate (di-Glu; โEE) motif** by using a **positively charged central pocket** at the center of its WD40 ฮฒ-propeller. file:human/DCAF12L2/DCAF12L2-deep-research-falcon.md A proteomics-focused source reports DCAF12L2 as a **CRL4 substrate receptor (CRL4^DCAF12L2)** and describes **affinity purificationโmass spectrometry (AP-MS)** evidence identifying **MEKK4** and the **WDR11 complex** as two independent substrate contexts; it further reports that **CRL4^DCAF12L2 mediates ubiquitylation of FAM91A1**, a component of the WDR11 complex. |
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Download this section (compressed HTML)Q: Does DCAF12L2 bind DDB1 directly? Given that it is an intronless retrocopy, has the WDXR motif required for DDB1 binding been conserved?
Q: What are the specific substrates of DCAF12L2? Does it share the C-terminal diglutamate degron recognition specificity of the parent gene DCAF12, or has it diverged to recognize different substrates?
Q: What is the biological role of DCAF12L2 in spermatogenesis? The testis-enriched expression pattern and X-linkage suggest a specialized reproductive function.
Q: Is there functional redundancy between DCAF12, DCAF12L1, and DCAF12L2? The DCAF12L1 knockout mouse showed no fertility defect, suggesting possible compensation.
Experiment: Co-immunoprecipitation of FLAG-tagged DCAF12L2 from HEK293T cells followed by immunoblotting for DDB1 and CUL4A/B. Compare with DCAF12 as positive control. If interaction is confirmed, reconstitute the complex in vitro for ubiquitination assays with candidate substrates.
Hypothesis: DCAF12L2 binds DDB1 and assembles into a functional CRL4 complex
Experiment: Generate DCAF12L2 knockout mice via CRISPR. Assess male fertility, testis histology, sperm count and morphology. Also generate DCAF12L1/DCAF12L2 double knockout to test for redundancy, given that the single DCAF12L1 knockout showed no phenotype.
Hypothesis: DCAF12L2 has a specialized role in spermatogenesis
Experiment: Express and purify recombinant DCAF12L2 WD40 domain. Test binding to synthetic peptides bearing C-terminal Glu-Glu motifs (MAGEA3, CCT5 C-terminal sequences) using fluorescence polarization. Compare affinity with DCAF12 to assess whether substrate specificity is conserved.
Hypothesis: DCAF12L2 recognizes C-terminal diglutamate degrons like DCAF12
What is not known โ curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: Whether DCAF12L2 directly binds DDB1/CUL4 and assembles into a functional CRL4 ubiquitin ligase complex remains unresolved.
OPEN BIOLOGYCURATION MF_DARK
What is known: DCAF12L2 is a WD40-repeat DCAF12-family protein with IBA support for membership in the Cul4-RING E3 ubiquitin ligase complex and thesis-level proteomics evidence for candidate CRL4^DCAF12L2 substrates. However, a separate assay reported no significant DDB1 binding for DCAF12L2, so the direct complex-assembly step is still unvalidated.
Significance: The current substrate-adaptor function depends on CRL4 assembly. Without direct DDB1/CUL4 engagement evidence, DCAF12L2 remains a family-inferred candidate rather than a biochemically established CRL4 substrate receptor.
What would resolve it: Orthogonal DCAF12L2-DDB1/CUL4 interaction assays in relevant cells and purified reconstitution, ideally including DDA1/cofactor conditions and comparison with DCAF12.
Provenance (the field's own admissions):
Gap: The direct substrates and degron-recognition rules of DCAF12L2 are not established. It is unknown whether DCAF12L2 recognizes DCAF12-like C-terminal acidic degrons or has diverged to a distinct substrate-recognition mode.
OPEN BIOLOGYCURATION MF_DARK
What is known: Parent DCAF12 has strong structural and biochemical evidence for C-terminal di-Glu degron recognition. For DCAF12L2, reported MEKK4 and WDR11/FAM91A1 substrate candidates come from limited proteomics/thesis-level evidence, while separate work reported no detectable binding to the DCAF12 substrate MCMBP.
Significance: Substrate specificity is the informative molecular function for a DCAF-family receptor. Until the substrates and degron rules are confirmed, DCAF12L2 should not be propagated to autophagy or named substrate-degradation terms by similarity alone.
What would resolve it: Validate candidate substrates with DCAF12L2-dependent ubiquitination/degradation assays, degron mutagenesis, and direct binding assays against DCAF12 di-Glu substrates and DCAF12L2-specific candidates.
Provenance (the field's own admissions):
Gap: The biological role of DCAF12L2 in testis-enriched or epididymal cell contexts is unknown.
OPEN BIOLOGY BP_DARK
What is known: DCAF12L2 is an X-linked intronless DCAF12 retrocopy with testis/epididymis-enriched expression evidence and conserved coding capacity, but no direct loss-of-function or substrate-based evidence connects it to spermatogenesis, fertility, or a specific germ-cell pathway.
Significance: Expression suggests the gene may have been retained for a reproductive function, but the relevant process, cell type, and substrate pathway remain undefined.
What would resolve it: DCAF12L2 perturbation in germ-cell or epididymal models, ideally with fertility, testis histology, substrate proteomics, and DCAF12/DCAF12L1 redundancy controls.
Provenance (the field's own admissions):
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