XPB (

xeroderma pigmentosum Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in sun- ...

type B) is an

ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals, men's professional tennis governing body * American Technical Publishers, employee-owned publishing company * ', a Danish pension * Armenia Tree Project, non ...

-dependent DNA helicase in humans that is a part of the TFIIH

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fu ...

complex.

Structure

The 3D-structure of the archaeal homolog of XPB has been solved by X-ray crystallography by Dr. John Tainer and his group at

The Scripps Research Institute Scripps Research, previously known as The Scripps Research Institute (TSRI), is a nonprofit American medical research facility that focuses on research and education in the biomedical sciences. Headquartered in San Diego, California, the institu ...

Function

XPB plays a significant role in normal basal transcription,

transcription coupled repair Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucleo ...

(TCR), and

nucleotide excision repair Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucle ...

(NER). Purified XPB has been shown to unwind DNA with 3’-5’ polarity. The function of the XPB(ERCC3) protein in NER is to assist in unwinding the DNA double helix after damage is initially recognized. NER is a multi-step pathway that removes a wide range of different DNA damages that distort normal base pairing. Such damages include bulky chemical adducts, UV-induced pyrimidine dimers, and several forms of oxidative damage. Mutations in the XPB(ERCC3) gene can lead, in humans, to

(XP) or XP combined with

Cockayne syndrome Cockayne syndrome (CS), also called Neill-Dingwall syndrome, is a rare and fatal autosomal recessive neurodegenerative disorder characterized by growth failure, impaired development of the nervous system, abnormal sensitivity to sunlight (photosen ...

(XPCS). Mutant XPB cells from individuals with the XPCS phenotype are sensitive to UV irradiation and acute oxidative stress.

Disorders

Mutations in XPB and other related complementation groups, XPA-XPG, leads to a number of genetic disorders such as

Xeroderma pigmentosum Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in sun- ...

, Cockayne's syndrome, and

trichothiodystrophy Trichothiodystrophy (TTD) is an autosomal recessive inherited disorder characterised by brittle hair and intellectual impairment. The word breaks down into ''tricho'' – "hair", '' thio'' – "sulphur", and ''dystrophy'' – "wasting away" or lit ...

Interactions

XPB has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

with: * BCR gene, *

CDK7 Cyclin-dependent kinase 7, or cell division protein kinase 7, is an enzyme that in humans is encoded by the ''CDK7'' gene. The protein encoded by this gene is a member of the cyclin-dependent protein kinase (CDK) family. CDK family members are h ...

, *

ERCC2 __NOTOC__ ERCC2, or XPD is a protein involved in transcription-coupled nucleotide excision repair. The XPD (ERCC2) gene encodes for a 2.3-kb mRNA containing 22 exons and 21 introns. The XPD protein contains 760 amino acids and is a polypeptide w ...

, * GTF2H1, *

GTF2H2 General transcription factor IIH subunit 2 is a protein that in humans is encoded by the ''GTF2H2'' gene. Function This gene is part of a 500 kb inverted duplication on chromosome 5q13. This duplicated region contains at least four genes and r ...

, * GTF2H4, *

GTF2H5 General transcription factor IIH subunit 5 is a protein that in humans is encoded by the ''GTF2H5'' gene. Function The ''GTF2H5(TTDA)'' gene encodes a small (71 amino acid) protein that stabilizes the multi-subunit transcription repair factor IIH ...

, * P53, *

PSMC5 26S protease regulatory subunit 8, also known as 26S proteasome AAA-ATPase subunit Rpt6, is an enzyme that in humans is encoded by the ''PSMC5'' gene. This protein is one of the 19 essential subunits of a complete assembled 19S proteasome complex ...

, and * XPC.

Small molecule inhibitors

Potent, bioactive natural products like triptolide that inhibit mammalian transcription via inhibition of the XPB subunit of the general transcription factor TFIIH has been recently reported as a glucose conjugate for targeting hypoxic cancer cells with increased glucose transporter expression.

References

External links

GeneReviews/NIH/NCBI/UW entry on Xeroderma Pigmentosum
* {{DEFAULTSORT:Xpb EC 3.6.4 DNA replication