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XPB is a gene that encodes a DNA-dependent ATPase and DNA helicase involved in DNA repair, transcription, and nucleotide excision repair. The protein is part of the TFIIH core complex, which is involved in transcription initiation and DNA repair. This complex is also responsible for the condition xeroderma pigmentosum, which is caused by mutations in the XPB gene.

Function

The XPB gene encodes a protein that is part of the TFIIH core complex. This complex is involved in the initiation of transcription and nucleotide excision repair (NER). The protein has ATPase and DNA helicase activities, which are essential for these processes.

In transcription, the TFIIH complex unwinds the DNA around the transcription start site, allowing the RNA polymerase to access the DNA template and begin synthesizing RNA. In NER, the complex unwinds the DNA around a damage site, allowing the damaged DNA to be excised and replaced with new DNA.

Clinical significance

Mutations in the XPB gene can cause xeroderma pigmentosum (XP), a rare genetic disorder characterized by extreme sensitivity to sunlight, skin cancer, and neurological problems. XP patients have a defect in their ability to repair DNA damage caused by ultraviolet (UV) light, which leads to the accumulation of DNA damage and the development of skin cancer.

There are several different types of XP, each caused by mutations in a different gene involved in NER. XPB is one of these genes. Mutations in XPB can also cause Cockayne syndrome, a disorder characterized by growth failure, impaired development of the nervous system, and premature aging.

See also

• DNA repair
• Transcription (genetics)
• Nucleotide excision repair
• Xeroderma pigmentosum
• Cockayne syndrome