TFIIH

TFIIH is a protein complex that plays a crucial role in several cellular processes, including transcription and DNA repair. It is composed of ten individual proteins and is one of several general transcription factors that make up the RNA polymerase II preinitiation complex.

Structure[edit | edit source]

TFIIH is a multi-subunit complex that consists of ten individual proteins. These proteins are organized into two sub-complexes: the core complex, which contains seven proteins, and the CDK-activating kinase (CAK) complex, which contains three proteins. The core complex includes the proteins XPB, XPD, p44, p52, p34, p62, and TTDA. The CAK complex includes the proteins CDK7, cyclin H, and MAT1.

Function[edit | edit source]

TFIIH has several functions in the cell, primarily related to transcription and DNA repair. During transcription, TFIIH is involved in the formation of the RNA polymerase II preinitiation complex, which is necessary for the initiation of transcription. TFIIH also has helicase and kinase activities, which are used to unwind the DNA double helix and phosphorylate the RNA polymerase II, respectively.

In addition to its role in transcription, TFIIH is also involved in nucleotide excision repair (NER), a process that removes damaged bases from the DNA. In NER, TFIIH unwinds the DNA around the damage and recruits other proteins to excise the damaged section and fill in the gap with new DNA.

Clinical significance[edit | edit source]

Mutations in the genes encoding the proteins of the TFIIH complex can lead to several rare genetic disorders, including xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy. These disorders are characterized by sensitivity to sunlight, premature aging, and neurological abnormalities, among other symptoms.