XPB is an ATP

Adenosine triphosphate

Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

 dependent human DNA helicase

Helicase

Helicases are a class of enzymes vital to all living organisms. They are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands using energy derived from ATP hydrolysis.-Function:Many cellular processes Helicases are a...

 that is a part of the TFIIH transcription factor complex.

Structure

The 3D structure of the archeael homologue of XPB has been solved by X-ray crystallography by Dr. John Tainer and his group at The Scripps Research Institute

The Scripps Research Institute

The Scripps Research Institute is an American medical research facility that focuses on research in the basic biomedical sciences. Headquartered in La Jolla, California, with a sister facility in Jupiter, Florida, the institute is home to 3,000 scientists, technicians, graduate students, and...

.

Function

XPB plays a significant role in normal basal transcription, transcription coupled repair (TCR), and nucleotide excision repair

Nucleotide excision repair

Nucleotide excision repair is a DNA repair mechanism. DNA constantly requires repair due to damage that can occur to bases from a vast variety of sources including chemicals, radiation and other mutagens...

 (NER). Purified XPB has been shown to unwind DNA with 3’-5’polarity.

Disorders

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

Xeroderma pigmentosum

Xeroderma pigmentosum, or XP, is an autosomal recessive genetic disorder of DNA repair in which the ability to repair damage caused by ultraviolet light is deficient. In extreme cases, all exposure to sunlight must be forbidden, no matter how small. Multiple basal cell carcinomas and other skin...

, Cockayne's syndrome, and Trichothiodystrophy.

Interactions

XPB has been shown to interact

Protein-protein interaction

Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...

 with XPC

XPC (gene)

Xeroderma pigmentosum, complementation group C, also known as XPC, is a protein which in humans is encoded by the XPC gene. XPC is involved in the recognition of bulky DNA adducts in nucleotide excision repair.- Function :...

, BCR gene

BCR gene

The BCR gene is one of the two genes in the bcr-abl complex, which is associated with the Philadelphia chromosome.-Pathology:...

, ERCC2

ERCC2

ERCC2, or XPD is a protein involved in transcription-coupled nucleotide excision repair.The XPD gene encodes for a 2.3-kb mRNA containing 22 exons and 21 introns. The XPD protein is a 760 amino acids polypeptide with a size of 87kDa...

, P53

P53

p53 , is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is crucial in multicellular organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer...

, GTF2H2

GTF2H2

General transcription factor IIH subunit 2 is a protein that in humans is encoded by the GTF2H2 gene.-Interactions:GTF2H2 has been shown to interact with GTF2H5, XPB and ERCC2.-Further reading:...

, GTF2H1

GTF2H1

General transcription factor IIH subunit 1 is a protein that in humans is encoded by the GTF2H1 gene.-Interactions:GTF2H1 has been shown to interact with E2F1, XPB, ERCC2, Estrogen receptor alpha, Cyclin-dependent kinase 7 and TCEA1....

, GTF2H5

GTF2H5

General transcription factor IIH subunit 5 is a protein that in humans is encoded by the GTF2H5 gene.-Interactions:GTF2H5 has been shown to interact with GTF2H2 and XPB.-Further reading:...

, Cyclin-dependent kinase 7

Cyclin-dependent kinase 7

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 family. CDK family members are highly similar to the gene products of Saccharomyces cerevisiae cdc28, and Schizosaccharomyces...

, PSMC5

PSMC5

26S protease regulatory subunit 8 is an enzyme that in humans is encoded by the PSMC5 gene.-Interactions:PSMC5 has been shown to interact with XPB, Sp1 transcription factor, PSMC3 and PSMC4.-Further reading:...

 and GTF2H4

GTF2H4

General transcription factor IIH subunit 4 is a protein that in humans is encoded by the GTF2H4 gene.-Interactions:GTF2H4 has been shown to interact with MED21, GTF2F1, TATA binding protein, XPB, POLR2A and Transcription Factor II B....

.

External links

• GeneReviews/NIH/NCBI/UW entry on Xeroderma Pigmentosum