You are examining the efficacy of a new potential anticancer drug. Addition of this drug to rapidly dividing cancer cells results in a blockade to progression through M-phase and the cells arrest at metaphase in the cell cycle. You determine that the drug targets a specific regulatory protein of cell cycle progression and show that it is which of the following proteins/complexes?
A) anaphase-promoting complex
B) cyclin D-CDK4/6
C) cyclin E-CDK2
D) E2F
E) securing

Question

Quizplus · Accepted Answer

The anaphase-promoting complex (APC) is responsible for triggering the transition from metaphase to anaphase by marking specific proteins for degradation. If the drug causes cells to arrest at metaphase, it likely inhibits the APC, preventing the progression to anaphase. The anaphase-promoting complex (APC) is a ubiquitin ligase that controls the levels of the M-phase cyclins as well as other regulators of mitosis. One important function of APC is to control the initiation of sister chromatid separation which begins at the metaphase-anaphase transition. The attachment of the sister chromatids to the opposite poles of the mitotic spindles occurs early during mitosis. The ability of the sister chromatids to be pulled apart is initially inhibited because they are bound together by a protein complex termed cohesin complex. The cohesin complex is deposited along the chromosomes as they are duplicated during S-phase. Anaphase can only begin with the disruption of the cohesin complex. The breakdown of the cohesin complex is brought about as a consequence of the activation of the ubiquitin ligase activity of the APC. APC targets a protein called securin. Securin functions to inhibit the protease called separase and the action of separase is to degrade the proteins of the cohesin complex, thus allowing sister chromatid separation.

You Are Examining the Efficacy of a New Potential Anticancer