Xeroderma pigmentosum group B-complementing protein
ATP-dependent 3'-5' DNA helicase, component of the core-TFIIH basal transcription factor, involved in nucleotide excision repair (NER) of DNA and, when complexed to CAK, in RNA transcription by RNA polymerase II. Acts by opening DNA either around the RNA transcription start site or the DNA damage.
Defects in ERCC3 are the cause of xeroderma pigmentosum complementation group B (XP-B) [MIM:610651]; also known as xeroderma pigmentosum II (XP2) or XP group B (XPB) or xeroderma pigmentosum group B combined with Cockayne syndrome (XP-B/CS). Xeroderma pigmentosum is an autosomal recessive pigmentary skin disorder characterized by solar hypersensitivity of the skin, high predisposition for developing cancers on areas exposed to sunlight and, in some cases, neurological abnormalities. Some XP-B patients present features of Cockayne syndrome, including dwarfism, sensorineural deafness, microcephaly, mental retardation, pigmentary retinopathy, ataxia, decreased nerve conduction velocities. Defects in ERCC3 are a cause of trichothiodystrophy photosensitive (TTDP) [MIM:601675]. TTDP is an autosomal recessive disease characterized by sulfur-deficient brittle hair and nails, ichthyosis, mental retardation, impaired sexual development, abnormal facies and cutaneous photosensitivity correlated with a nucleotide excision repair (NER) defect. Neonates with trichothiodystrophy and ichthyosis are usually born with a collodion membrane. The severity of the ichthyosis after the membrane is shed is variable, ranging from a mild to severe lamellar ichthyotic phenotype. There are no reports of skin cancer associated with TTDP.
Belongs to the helicase family. RAD25/XPB subfamily. Contains 1 helicase ATP-binding domain. Contains 1 helicase C-terminal domain.