This is a manually prepared literature and database synthesis. Automated research-provider attempts did not return a usable report. It is not attributed to an automated provider. The source guide distinguishes actual original reads from unavailable experiments and records operative locators.
Human XPG is a structure-specific DNA endonuclease. Purified full-length protein recognizes DNA bubbles and junctions, with contacts on both duplex DNA and a short single-stranded overhang. Footprinting and competition assays establish the junction preference; they do not imply strong general affinity for isolated single- or double-stranded DNA. The original human biochemical work also demonstrates internal cleavage of covalently closed ssDNA. Different substrate geometries give different cleavage positions, so the supported catalytic class is broader than a flap-only or exclusively duplex-only enzyme. PMID:12644470(https://doi.org/10.1074/jbc.M213155200), PMID:8078765(https://pmc.ncbi.nlm.nih.gov/articles/PMC523723/?page=0), PMID:32522879(https://pmc.ncbi.nlm.nih.gov/articles/PMC7321962/).
Structural reagents require careful interpretation. One study replaces human residues 79–785 with an archaeal FEN segment and truncates the C terminus; the engineered XPGcat reagent differs from full-length XPG in bubble incision. Another links human residues 1–112 and 750–990 and studies synthetic splayed-arm DNA. These constructs illuminate the catalytic architecture but are neither complete XPG nor its two natural shorter splice products. Full-length assays, mutant controls and structural-fragment assays are considered separately. PMID:32522879, supplementary Online Methods, PMID:32821917(https://pmc.ncbi.nlm.nih.gov/articles/PMC7515719/).
XPG performs the 3′ incision of nucleotide-excision repair. Human factor reconstitution and functional immunoprecipitates establish executed repair activity, while salt sensitivity and weak associations argue against assuming that every factor belongs to a permanently preassembled complex. Current human Reactome records identify full-length P28715 as the active DNA endonuclease in both global-genome and transcription-coupled repair incision reactions. Neighboring polymerase, ligase and ERCC1–ERCC4 reactions remain activities of their own components. PMID:11259578(https://pmc.ncbi.nlm.nih.gov/articles/PMC86862/), GG-NER incision, TC-NER incision.
The conserved factor-3 assembly has actual yeast Rad2–TFIIH purification and NER-reconstitution evidence. Human experiments independently support XPG–TFIIH association and stimulation. In the human study, full-length XPG was expressed in insect cells and crosslinked in a repair assembly; XPG itself was absent from the final cryo-EM density. Main-text crosslink assignments support contacts with XPD and XPB, but do not establish every possible TFIIH subunit pair. The assembly does not make XPG a helicase or a constitutive transcriptional TFIIH subunit. PMID:8855246(https://pmc.ncbi.nlm.nih.gov/articles/PMC38221/), PMID:31253769(https://pmc.ncbi.nlm.nih.gov/articles/PMC6599211/).
In human cells, XPG associates with BRCA1 and with BRCA2/PALB2/RAD51/DSS1 assemblies. Repair-factor recruitment and a DR-GFP gene-conversion assay support a non-catalytic contribution to homologous recombination, beyond a nonspecific viability phenotype. These experiments do not assign strand-exchange catalysis to XPG. Nuclear repair foci and fractionation support a chromatin-associated context, with the explicit limitation that P100 also contains nuclear matrix and other insoluble material. PMID:26833090(https://pmc.ncbi.nlm.nih.gov/articles/PMC4761302/).
Biochemical NTHL1 experiments demonstrate an activating role for XPG through association, increased substrate binding and increased incision product. The combined glycosylase/AP-lyase readout does not separately measure the rate of AP-site formation. NTHL1 performs base removal; XPG is an activating partner. The paper’s discussion model for transcription-coupled BER is not treated as an experimentally established XPG pathway mechanism. The separate retracted background report is not used as supporting evidence. PMID:9927729, Figures 1–3.
PCNA association, GADD45A association in the recovered supplement, self-association under defined biochemical conditions, and human fibroblast responses to UVC are supported with their assay limits. They do not establish additional intrinsic enzyme activities. Wild-type XPG complementation can suppress the measured UV-induced apoptotic response, although the proximal mechanism and the behavior of catalytic mutants require context. PMID:9305916(https://doi.org/10.1074/jbc.272.39.24522), PMID:17268471 supplementary data, PMID:10026181(https://doi.org/10.1074/jbc.274.9.5637), PMID:16167068(https://doi.org/10.1038/sj.cdd.4401764).
The canonical product contains 1,186 residues. The two reported splice products contain 419 and 232 residues, with distinct source-defined sequence edits. Their expression, localization and function cannot be inferred from engineered deletion mutants or the full-length biochemical assays. The review preserves all three product identities without blanket functional equivalence.
Specific RNA polymerase II/CSB/p62/p44 claims remain source-limited, the exact ERCC5–BRAF supplementary screen record remains unverified, and the original RPA-associated experiment remains inaccessible. Broad TC-NER participation is independently supported by XPG’s executed incision step; this does not resolve the unavailable upstream interaction assays. Similarly, the damaged-DNA binding assertion is not inferred merely from an NER role or a synthetic DNA-junction structure. These uncertainties are retained explicitly rather than treated as evidence that the curator’s assertion was wrong.