Promoter clearance by RNA polymerase II

► Pol II must break promoter and factor interactions to enter transcript elongation. ► Abortive initiation is not extensive for pol II. ► Clearance is driven by TFIIH and collapse of the initial transcription bubble. ► Pol II early elongation complexes backtrack, even after RNA exits the polymerase. ► Clearance is incomplete until the pol II elongation complex is fully stabilized.