Practice question

Embryonic stem cell pluripotency depends critically on autoregulatory loop of Oct4, Sox2, and Nanog binding their own and each other's promoters and enhancers of downstream Esrrb, Klf4, Utf1 and chromatin modifiers. These factors recruit Mediator complex and p300 acetyltransferase to maintain open accessible euchromatin at pluripotency loci. p53, a prominent DNA damage sensor, induces cell cycle arrest, apoptosis, and differentiation by activating p21, Bax, and repressing Nanog transcription. Pharmacological inhibition or temporary genetic deletion of p53 dramatically increases somatic reprogramming efficiency, confirming its role as tumor suppressor antagonizing self-renewal rather than supporting network.