Refer to the figure below. The figure shows a signal transduction pathway involving two proteins found in the cytoplasm—JAK and STAT.Based on this figure, what are the roles of JAK and STAT in this pathway?
A) JAK is a G protein and STAT is a transcription factor.
B) JAK is a transcription factor and STAT is a GTPase.
C) JAK is a protein kinase and STAT is a G protein.
D) JAK is a G protein and STAT is adenylyl cyclase.
E) JAK is a protein kinase and STAT is a transcription factor.

Question

Refer to the figure below.  The figure shows a signal transduction pathway involving two proteins found in the cytoplasm—JAK and STAT.Based on this figure, what are the roles of JAK and STAT in this pathway?
A) JAK is a G protein and STAT is a transcription factor. 
B) JAK is a transcription factor and STAT is a GTPase. 
C) JAK is a protein kinase and STAT is a G protein. 
D) JAK is a G protein and STAT is adenylyl cyclase. 
E) JAK is a protein kinase and STAT is a transcription factor.

Quizplus · Accepted Answer

Based on the figure, JAK is shown to phosphorylate (add a phosphate group to) STAT, indicating that JAK is a protein kinase. STAT is then shown to enter the nucleus and act as a transcription factor, indicating that STAT plays a role in regulating gene expression. Therefore, the correct answer is E, with JAK as a protein kinase and STAT as a transcription factor.

Refer to the Figure Below