Recruits TFIIH to the initiation complex and stimulates the RNA polymerase II C-terminal domain kinase and DNA-dependent ATPase activities of TFIIH. Both TFIIH and TFIIE are required for promoter clearance by RNA polymerase. Tetramer of two alpha and two beta chains (PubMed:1956398). Interacts with FACT subunit SUPT16H (PubMed:10792464). Interacts with ATF7IP (PubMed:19106100). Interacts with SND1 (PubMed:7651391). The disease is caused by variants affecting the gene represented in this entry. Belongs to the TFIIE beta subunit family.