When unfolded proteins accumulate in the lumen of the endoplasmic reticulum due to inefficient folding conditions, a membrane-bound protein kinase is activated and phosphorylates a subunit of the translation initiation factor eIF2. Indicate which of the following events would (Y) or would not (N) occur as a result. Your answer would be a four-letter string composed of letters Y and N only, e.g. YYYY.
( ) eIF2 binds tightly to the ribosome.
( ) Translation initiation is stimulated.
( ) The GDP-bound form of eIF2 accumulates.
( ) eIF2B is activated.

Question

When unfolded proteins accumulate in the lumen of the endoplasmic reticulum due to inefficient folding conditions, a membrane-bound protein kinase is activated and phosphorylates a subunit of the translation initiation factor eIF2. Indicate which of the following events would (Y) or would not (N) occur as a result. Your answer would be a four-letter string composed of letters Y and N only, e.g. YYYY.
( )	eIF2 binds tightly to the ribosome.
( )	Translation initiation is stimulated.
( )	The GDP-bound form of eIF2 accumulates.
( )	eIF2B is activated.

Quizplus · Accepted Answer

Under stress conditions, eIF2 phosphorylation prevents its release from the guanine nucleotide exchange factor eIF2B, sequestering the latter in a nonfunctional form, and consequently preventing further eIF2 guanine nucleotide exchange and activation. As a result, translation initiation is largely inhibited.

When Unfolded Proteins Accumulate in the Lumen of the Endoplasmic