Acts as component of the general transcription and DNA repair factor IIH (TFIIH or factor B), which is essential for both basal and activated transcription, and is involved in nucleotide excision repair (NER) of damaged DNA. TFIIH has CTD kinase and DNA-dependent ATPase activity, and is essential for polymerase II transcription in vitro. Component of the transcription factor IIH (TFIIH) holo but not the TFIIH core complex. Component of a complex consisting of KIN28, CCL1 and TFB3; the KIN28-CCL1 dimer is known as the TFIIK complex. Present with 3050 molecules/cell in log phase SD medium.