XPD Helicase (3CRV)

From Proteopedia

Revision as of 18:15, 10 April 2016

XPD Helicase

Function

XPD Helicase is esential in nucleotide excsision repair (NER), which is a DNA repair mechanims that removes DNA damaged from ultraviolet light (UV). UV light prduces bulky DNA adducts, more specifically, thymine dimers, which interfere with base pairing during DNA replication. The resulting gap from the removed DNA is rplaced by DNA polymerase. XPD Helicase is also one of the nine subunits of transcription factor II Human (TFIIH). A part of TFIIH, XPD has the resposnisibility of enzymaticalaly initatiating transcription by melting the promoter region, which is an ATP-dependednt process. -Required for nucleotide excision repair (NER) as part as transcription factor/repair complex TFIIH

-Critical for helicase activity and stability and the TFIIH complex

-DNA helicase is essential during DNA replication because it unwinds the two strands at places called origins, where synthesis is initiated. This allows both strands of DNA to be replicated. XPD helicase activity is essential for NER but dispensable for transcription

-NER removes DNA damaged by ultraviolet light

Disease

Mutations in XPD Helicase are associated with three distinct diseases: Cockayne Syndrome (CS), Xeroderma Pigmentosum (XP), and trichothiodystrophy (TTD). The common symptom between these diseases is sensitivity to UV light because of defects in the repair system that fixes mutations caused by UV radiation. CS is characterized by short stature, signs of premature aging, failure to gain weight, impaired development of the nervous system, and photosensitivity. XP is characterized by extreme sensitivity to sunlight and a higher risk of skin cancer. TTD is characterized by sparse and brittle hair, pregnancy-induced high blood pressure, intellectual disabilities, a higher risk of recurrent respiratory infections, and photosensitivity.

Relevance

Structural highlights

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References

1. Fan, L., Fuss, J. O., Cheng, Q. J., Arvai, A. S., Hammel, M., Roberts, V. A., Cooper, P. K., and Tainer, J. A. (2008) XPD helicase structures and activities: Insights into the cancer and aging phenotypes from XPD mutations.

2. Cleaver, J. E., Lam, E. T., and Revet, I. (2009) Disorders of nucleotide excision repair: The genetic and molecular basis of heterogeneity. Nat. Rev. Genet. 10, 756-768.

3.Nance, M. A., and Berry, S. A. (1992) Cockayne syndrome: Review of 140 cases. Am. J. Med. Genet. 42, 68-84.