Question

The role that p53 protein plays in suppressing inappropriate progression through the cell cycle depends on all of the following EXCEPT _______.a. p53 activates transcription of WAF1b. p53 indirectly blocks G1 to S transition in the cell cyclec. the ability of p53 to bind DNA lesionsd. p53 stability increases in the presence of unrepaired DNA lesions.

Answer 1

Answer:

a. p53 activates transcription of WAF1.

Explanation:

WAF1 transcription occurs independent of p53 during oxidative stress so p53 does not play any role in cell cycle arrest in the signaling pathway which involves WAF1 .

In rest of the mentioned options, p53 plays a role directly or indirectly. During double stranded lesion in DNA in G1 phase, a sensor protein known as ATM binds the DNA lesion site. ATM is a serine/threonine kinase which phosphorylates another kinase known as chk2. After phosphorylation, chk2 stabilizes transcription factor p53. p53 further acts as a transcription factor for the synthesis of a protein known as p21 which inhibits G1 phase specific CDK and ultimately cell is arrested in G1 phase. The cell remains in arrested state until the DNA lesion is fully repaired. Hence, p53 indirectly blocks G1 to S transition with the help of p21.

As such WAF1 transcription factor involving pathway also requires p21 protein for causing cell cycle arrest but in this pathway p21 is not synthesized with the help of p53.