Regulation of the Ci (Cubitus interruptus) protein in the Hedgehog signaling pathway is reminiscent of that of β-catenin in the Wnt pathway. Which of the following features is shared among these two proteins?
A) Both proteins are ubiquitylated when the signal (Hedgehog or Wnt) is present.
B) Both proteins are able to enter the nucleus only in the absence of the signal.
C) Both proteins can be phosphorylated by GSK3 and CK1 in the absence of the signal.
D) Both proteins are fully degraded by the proteasome in the absence of the signal.
E) None of the above.

Question

Quizplus · Accepted Answer

Both Ci and β-catenin are phosphorylated by GSK3 and CK1 in the absence of stimulation in Hedgehog and Wnt signaling pathways, respectively. They are both ubiquitylated and undergo proteolysis in the absence of signal. β-catenin is stabilized and can enter the nucleus only in the presence of Wnt. Ci enters the nucleus in the presence of Hedgehog and acts as a transcriptional activator, but its fragment (produced from partial proteolysis) can also enter the nucleus and act as a transcriptional repressor in the absence of signal.

Regulation of the Ci (Cubitus Interruptus) Protein in the Hedgehog