Formation of a stable dimer of CDK7/cyclin H requires phosphorylation on a conserved threonine (Thr170) in the activation loop of CDK7 and is essential for activity (human cervical tumor cell line–HeLa; human lung small cell carcinoma cell line–H1299; insect cells–SF9) [54,55,56]. The gene discussed is CDK7; the disease is small cell lung carcinoma.