You are analyzing the cause of mutations in CREB signaling. For each set of cond
ID: 256760 • Letter: Y
Question
You are analyzing the cause of mutations in CREB signaling. For each set of conditions, describe a mutation that could be the cause (be sure to state which gene or regulatory element is mutated, and how the mutation disrupts the function of the gene).
a. cAMP levels are high, G protein is in the cytoplasm, Protein kinase A is in the cytoplasm, and CREB is not phosphorylated and is not bound to the enhancer.
b. cAMP levels are low, G protein is in the cytoplasm, Protein kinase A is in the cytoplasm, and CREB is not phosphorylated and is not bound to the enhancer.
Explanation / Answer
Answer a) Since G proteins are in cytoplasm and cAMP levels are high, it means that secondary messenger are produced which will activate the protein kinase A (PKA). Once the PKA is activated, it translocate to nucleus to active CREB by phosphorylation. But the PKA is in cytoplasm that means the PKA is either not activate or not able to translocate to nucleus indicating that this gene is mutated.
Answer b) Since G proteins are in cytoplasm but cAMP levels are low indicating that secondary messengers are not produced by break down of ATP by Adenylate cyclase. This suggest that Adenylate cyclase is mutated so cAMP is not produced and PKA is activated so present in cytoplasm and not able to translocate in nucleus to phosphorylate CREB.
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