MAT1 is an assembly/targeting factor for cyclin-dependent kinase-activating kinase (CAK), which interacts with the transcription factor TFIIH [1]. The domain found to the N-terminal side of this domain is a C3HC4 RING finger [1].

1: Solution structure of the N-terminal domain of the human TFIIH MAT1 subunit: new insights into the RING finger family. Gervais V, Busso D, Wasielewski E, Poterszman A, Egly JM, Thierry JC, Kieffer B; J Biol Chem 2001;276:7457-7464. PMID:11056162