XPB

• OMIM: 133510
• UniProt: P19447

The TFIIH - XPB helicase is the enzyme in the nucleus of eukaryotic cells, which as part of the transcription factor IIH ( TFIIH ) the opening of the DNA duplex catalyzed after the pre-initiation complex was assembled. This reaction step is part of the initiation of transcription of all eukaryotic genes. In addition, XPB plays a similar role in DNA repair. Mutations in the human ERCC3 gene coding for XPB, can contribute rare genetic disorder xeroderma pigmentosum type B lead, in which the risk of skin cancer is increased 2000-fold, or Tay syndrome, a rare ichthyosis.

The opening of the double strand consumes one molecule of ATP and spans the bases from -10 to 2 relative to the Genanfangs. She is supported by untwisting of the DNA ( referred to as negative supercoiling ) using TFIIE. At the DNA repair also takes part in the XPD helicase. Open the DNA is referred to in both cases as a DNA bubble.

An orthologous to XPB protein was found in archaea. The XPB has found as the eukaryotic in vitro, no helicase activity. The protein is a function assumed for the DNA repair.

XPB and XPD after make a part of the defense of the cell against retroviral infection, a laboratory study. A Chinese study found that a combination of certain XPB and XPD - variants increased the risk of lung cancer.

Further Reading

• Beck BD, Hah DS, Lee SH: XPB and XPD in between transcription and DNA repair. In: Adv Exp Med Biol 637, 2008, pp. 39-46. . PMID 19,181,109th
• Coin F, Oksenych V, Egly JM: Distinct roles for the XPB/p52 and XPD/p44 subcomplexes of TFIIH in damaged DNA opening falling on nucleotide excision repair. In: Mol Cell. 26, No. 2, April 2007, pp. 245-56. doi: 10.1016/j.molcel.2007.03.009. PMID 17,466,626th
• Hu GM, Liu LM, Zhang JX, et al.: The role of XPB in cell apoptosis and viability and its relationship with p53, p21 ( Waf1/Cip1 ) and c -myc in hepatoma cells. In: Dig Liver Dis. 38, No. 10, October 2006, pp. 755-61. doi: 10.1016/j.dld.2006.06.009. PMID 16,914,395th