Distinct regions of MAT1 regulate cdk7 kinase and TFIIH transcription activities

The transcription/DNA repair factor TFIIM may be resolved into at least two subcomplexes: the core TFIIH and the cdk-activating kinase (CAR) complex. The CAK complex, which is also found free in the cell, is composed of cdk7, cyclin H, and MAT1. In the present work, we found that the C terminus of M AT1 binds to the cdk7 cyclin Ii complex and activates the cdk7 kinase activ ity. The median portion of MAT1, which contains a coiled-coil motif, allows the binding of CAK to the TFIIH core through interactions with both XPD an d XPB helicases. Furthermore, using recombinant TFIIH complexes, it is demo nstrated that the N-terminal RING finger domain of MAT1 is crucial for tran scription activation and participates to the phosphorylation of the C-termi nal domain of the largest subunit of the RNA polymerase II.