The CCNT family includes two C-type cyclins, cyclin-T1 (CCNT1) and cyclin-T2 (CCNT2), both of which are regulatory subunits of the cyclin-dependent kinase pair (CDK9/cyclin-T) complex, also called positive transcription elongation factor B (P-TEFb), which is proposed to facilitate the transition from abortive to productive elongation by phosphorylating the CTD (C-terminal domain) of the large subunit of RNA polymerase II (RNA Pol II). Members in this family contain two cyclin boxes. This model corresponds to the second one. The cyclin box is a protein binding domain.
Feature 1:AF4 family member binding site [polypeptide binding site]
Evidence:
Structure:4OR5: Human cyclin-T1 in complex with AFF4; contacts at 4A - View structure with Cn3D
Comment:P-TEFb (CDK9/cyclin T) is also a component of the super elongation complex (SEC) comprised of an AF4 family member AFF1 or AFF4, AF9/ENL, ELL1/2/3, and EAF1/2.
Lu S et al.(2020). "CDD/SPARCLE: the conserved domain database in 2020.",