cellular biology wiz needed 1) The cell cycle progresses via the activation of C
ID: 214604 • Letter: C
Question
cellular biology wiz needed
1) The cell cycle progresses via the activation of CDKs during different stages of the cell cycle. CDKs are activated when they bind to cyclins, which are expressed and then degraded at the appropriate times. However, checkpoint proteins, including Wee1 kinase, can modify CDKs when they are bound to cyclins to inhibit their activity and delay cell cycle progression. Wee1 phosphorylates and inhibits the activity of CDK1, an M-phase CDK whose activity is required for progress from S/G2 to M-phase How does a cell inhibit Wee1, and how does this lead to a feed forward mechanism that enables progression to M-phase? (2 points) a) b) When cancer cells are treated with Wee1 inhibitors, they often die. Why would inhibition of Wee1 lead to cancer cell death? (3 points)Explanation / Answer
a) Wee1 phosphorylate tyrosine residue of CDK1 which inhibit its activity. This inhibitory phosphate is remove by Cdc 25 phosphatase. A decrease in Wee1 activity and increase in Cdc 25 activity , resulting in activation of CDK. Full activation of cyclin CDK complex occur when a CDK activating kinase phosphorylate activating tyrosine residue near the CDK active site. In this manner cell progress from S/G2 to M phase.
b) Wee1 act as negative regulator of cyclin/ CDK1. It act as checkpoint to regulate entry of cell in M phase. Wee1 inhibitor promote cancer cell to bypass the cell cycle checkpoint and prematurely enter mitosis. It also delayed mititic exit because cell arrest at metaphase and take longer time to go to anaphase. This early entry and delayed exit lead to cell death. Wee1 inhibitor also act as antimitotic agent.
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