Which of the Following Scenarios May Contribute to the Hyperphosphorylation

Question

Which of the following scenarios may contribute to the hyperphosphorylation of pRb? A)Inactivation of the Ras pathway B)Inactivation of p21^Cip1 C)Activation of p15^INK4B D)Inactivation of NF-κB E)Activation of Smad3/4

Accepted Answer

p21^Cip1 is a cyclin-dependent kinase inhibitor that prevents the phosphorylation of pRb. Inactivation of p21^Cip1 would lead to increased activity of cyclin-dependent kinases, resulting in hyperphosphorylation of pRb.