How does the tumor suppressor protein p53 primarily respond when extensive double-stranded DNA damage is detected during the G1 phase?
Answer and explanation
Correct answer: D. It transcribes p21 (CDKN1A)
Following DNA damage, p53 is phosphorylated and stabilized, functioning as a transcription factor that upregulates p21. The p21 protein binds and inhibits cyclin D-CDK4/6 and cyclin E-CDK2 complexes, preventing phosphorylation of the retinoblastoma protein (Rb) and arresting cells in G1 to allow DNA repair, or inducing apoptosis via BAX if damage is irreparable. It does not directly polymerize tubulin or phosphorylate ligases.
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