A genetic variant of the retinoblastoma protein, called PSM-RB (phosphorylation

Question

A genetic variant of the retinoblastoma protein, called PSM-RB (phosphorylation site mutated RB), is not able to be phosphorylated by the action of CDK4/cyclinD1 complex. PSM-RB is said to have a constitutive growth-suppressing action on the cell cycle.

Problem 16.10 A genetic variant of the retinoblastoma protein, called PSM-RB (phosphorylation site mutated RB), is not able to be phosphorylated by the action of CDK4/cyclinD1 complex. PSM-RB is said to have a constitutive growth-suppressing action on the cell cycle. Part A Which of the following will be true in a cell with PsM-RB? Select all that apply. O pRB will always be phosphorylated. O pRB will never be phosphorylated. O pRB will always be bound to E2F transcription factor. O E2F transcription factor will always be bound to DNA. O CDK4 will never be bound to cyclin D1 O The cell will be stuck in G1 phase and never progress to S phase. O The cell will always pass the G1 checkpoint and progress to S phase. Submit My Answers Give Up

Explanation / Answer

pRB in its active state is bound to the transcription factor E2F. When the cell is ready to enter the next cycle, pRB gets phosphorylated which inactivates it and the cell enters the S phase from G1 phase.

In case of PSM-RB, the phosphorylation site is mutated and therefore will remain unphosphorylated. This implies that:

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