The second core now records GO:0004842 ubiquitin-protein transferase activity under contributes_to_molecular_function. The existing annotation (zero-based index 72; IDA, PMID:12732143) already uses contributes_to and remains accepted. DDB2 recognizes damaged DNA and helps target the CRL4 complex; the correction does not assign independent ubiquitin-transfer catalysis to DDB2 or add a new annotation. All source qualifiers, reference identifiers, product records and annotation decisions are preserved.
The PMID:12732143 abstract reports ubiquitin ligase activity in assembled DDB2/DDB1/CUL4A/ROC1 complexes. Its original assay text was not accessible during this focused correction. In the original PMID:16473935(https://pmc.ncbi.nlm.nih.gov/articles/PMC1413840/) Methods and Results, human normal and XP-E cell comparisons show DDB2-dependent complex recruitment to UV-damaged chromatin and changes in H2A ubiquitination. Native-chromatin co-immunoprecipitation establishes association in that context, not isolated DDB2-catalyzed transfer or purified binary DDB2–H2A binding.
The original PMID:19109893(https://pmc.ncbi.nlm.nih.gov/articles/PMC2676164/) structure study distinguishes human and zebrafish DDB2 complexes. DDB2 makes the damaged-DNA contacts; the relationship to the ubiquitination zone is explicitly a structural model. The human construct comprises residues 10–427 and was expressed with DDB1 in insect cells. That experiment does not establish equivalent function of all five natural products. The PMID:14751237 abstract specifically reports dominant-negative repair effects for D1/D2, while the full paper remained inaccessible. No new function is assigned to D3/D4. Original publication cache bytes and availability flags remain unchanged despite additive access to the two PMC originals.
The actual current GO:0004842 definition describes ubiquitin transfer; the schema provides the contribution slot for a subunit's role in a complex-level activity. GO:1990756, ubiquitin-like ligase-substrate adaptor activity, was considered but not newly assigned in this focused change: its complete binding assertion needs its own source assessment. The existing 18 generic protein-binding annotations remain non-core under the standing project curation instruction.
The annotation referred to positionally in the earlier entry is identified stably as GO:0004842 / IDA / PMID:12732143, with its existing contributes_to qualifier. The earlier entry is preserved unchanged.
The Methods/Results details above were checked against separately recovered original PMC HTML, accessed on 17 October 2026. Both repository publication caches remain abstract-only; their availability flags describe those cached files and do not replace the original-source reading recorded here.
The chromatin study original, Methods on cell lines and native chromatin preparation, identifies normal human and XP-E lymphoblastoid cells and states [PMID:16473935 “Coimmunoprecipitation from uncrosslinked chromatin was used to test for a physical interaction”]. The immunoprecipitation Methods specify the DDB1/DDB2 antibody procedure; the native-chromatin Results and Figure 5 describe the H2A/uH2A comparisons. These are complex-association measurements in human chromatin, with the limitations stated above.
The structure study original, Methods on protein production, lists [PMID:19109893 “hsDDB1 (1-1140), hsDDB2 (10-427) and drDDB2 (94-457)”] and specifies “High Five insect cells”. The opening structure Results distinguish human DDB1 paired with human or zebrafish DDB2: the 6-4 photoproduct complex uses zebrafish DDB2, while THF complexes are reported for both DDB2 species. It explicitly says “our discussion will focus on the high resolution zebrafish”. Thus the human expression construct is not presented as the species identity of every DNA-bound structure. No activity, product equivalence or additional GO assertion is inferred from these provenance details.