Cdk-activating kinase assembly factor MAT1/Tfb3 (IPR004575)

Short name: MAT1/Tfb3

Overlapping homologous superfamilies


Family relationships



MAT1/Tfb3 acts as component of the general transcription and DNA repair factor IIH (TFIIH), which is essential for both basal and activated transcription, and is involved in nucleotide excision repair (NER) of damaged DNA [PMID: 9235928]. It is a RING finger protein with a characteristic C3HC4 motif located in the N-terminal domain. MAT1/Tfb3 stabilises the cyclin H-CDK7 complex to form a functional CDK-activating kinase (CAK) enzymatic complex which then goes on to activate many of the CDK enzymes intimately involved in the cell cycle [PMID: 11007478]. CDK7 forms a stable complex with cyclin H and MAT1/Tfb3 in vivo only when phosphorylated on either one of two residues (Ser164 or Thr170) in its T-loop. The requirement for MAT1/Tfb3 for the activation of CAK can be by-passed by the phosphorylation of CDK7 on the T-loop. The two mechanisms for CDK7 complex stabilisation and activation (MAT1 addition and T-loop phosphorylation), which can operate independently in vitro, actually cooperate under physiological conditions to maintain complex integrity. With prolonged exposure to elevated temperature, dissociation to monomeric subunits occurs in vivo when CDK7 is dephosphorylated, even in the presence of MAT1/Tfb3 [PMID: 11447116].

GO terms

Biological Process

GO:0006289 nucleotide-excision repair
GO:0045737 positive regulation of cyclin-dependent protein serine/threonine kinase activity

Molecular Function

GO:0061575 cyclin-dependent protein serine/threonine kinase activator activity

Cellular Component

GO:0005675 transcription factor TFIIH holo complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.