You have synchronized a culture of HeLa cells so that the cells are all at the same stage in the cell cycle. You then treat the cells with serum containing nutrients and growth factors in the presence or absence of the drug rapamycin. The distribution of cell sizes in the two cell populations is shown below. Based on these results, do you think rapamycin is an activator or inhibitor of the TOR complex? Is the S6 kinase expected to be up-regulated or down-regulated in the presence of rapamycin?
A) Activator; up-regulated
B) Activator; down-regulated
C) Inhibitor; up-regulated
D) Inhibitor; down-regulated Answers

Question

You have synchronized a culture of HeLa cells so that the cells are all at the same stage in the cell cycle. You then treat the cells with serum containing nutrients and growth factors in the presence or absence of the drug rapamycin. The distribution of cell sizes in the two cell populations is shown below. Based on these results, do you think rapamycin is an activator or inhibitor of the TOR complex? Is the S6 kinase expected to be up-regulated or down-regulated in the presence of rapamycin? 
A) Activator; up-regulated 
B) Activator; down-regulated 
C) Inhibitor; up-regulated 
D) Inhibitor; down-regulated Answers

Quizplus · Accepted Answer

Rapamycin inhibits the mammalian TOR complex that is activated in response to growth factors in a PI 3-kinase-dependent manner. As a result, cell growth is retarded in a number of ways, including by inhibition of TOR-mediated activation of S6 kinase.

You Have Synchronized a Culture of HeLa Cells So That