Outside of the S phase of the cell cycle, the shelterin complex subunit TERF2 (TRF2) is phosphorylated on serine residue S365. This phosphorylation is performed by the complex of CDK2 and cyclin A (CCNA). Phosphorylation of TERF2 at S365 prevents association of RTEL1 with telomeres, thus protecting t-loops from promiscuous unwinding and inappropriate activation of ATM (Sarek et al. 2019).
Van Ly, D,