XPB, a subunit of TFIIH, is a target of the natural product triptolide.
Titov DV, Gilman B, He QL, Bhat S, Low WK, Dang Y, Smeaton M, Demain AL, Miller PS, Kugel JF, Goodrich JA, Liu JO. XPB, a subunit of TFIIH, is a target of the natural product triptolide. Nat Chem Biol. 2011 Mar; 7(3):182-8.