Activated STATs can induce the expression of SOCS proteins, which in turn inhibit the JAK-dependent phosphorylation of the STATs. Under sustained serum stimulation of mouse fibroblast cells, a number of oscillations can be observed as a consequence of this delayed negative feedback loop, as shown in the following simplified graph. According to this graph, approximately how long is the delay in the feedback response, and what process is mainly responsible for it?
A) 1 hour; transcription
B) 2 hours; transcription
C) 1 hour; mRNA export
D) 1 hour; mRNA translation
E) 2 hours; mRNA translation

Question

Activated STATs can induce the expression of SOCS proteins, which in turn inhibit the JAK-dependent phosphorylation of the STATs. Under sustained serum stimulation of mouse fibroblast cells, a number of oscillations can be observed as a consequence of this delayed negative feedback loop, as shown in the following simplified graph. According to this graph, approximately how long is the delay in the feedback response, and what process is mainly responsible for it? 
A) 1 hour; transcription 
B) 2 hours; transcription 
C) 1 hour; mRNA export 
D) 1 hour; mRNA translation 
E) 2 hours; mRNA translation

Quizplus · Accepted Answer

The major contribution to the delay appears to be that of mRNA export from the nucleus to the cytosol, corresponding to the lag in the solid gray curve compared to the dashed black curve. The former curve peaks about an hour after the latter.

Activated STATs Can Induce the Expression of SOCS Proteins, Which