Question

U937D cells express high levels of creatine kinase (CK‑B) mRNA but do not translate the mRNA into protein. Ribosomes bind the 5' end of the CK‑B mRNA; however, translation into protein is repressed in these cells. U937D cells synthesize the CK‑B enzyme when researchers introduce numerous short segments of RNA containing 3' UTR consensus sequences into the cells. The total amount of CK‑B mRNA does not change after adding RNA containing 3' UTR sequences. Introducing short RNA segments without the 3' UTR consensus sequences does not stimulate CK‑B synthesis. Which of the statements explains how the introduction of short RNA containing 3' UTR sequences allows CK‑B translation in U937D cells?.Explain how the introduction of short segments of RNA containing the 3'UTR sequences might remove the inhibition.

Answer 1

Answer:

Basically the translation of CK-B protein is inhibited in the U937D cells, despite the fact that the CK-B protein is bounded to the ribosomes. This is because(mechanisms) the translation is inhibited by the binding of translational repressors to the 3’UTR of the CK-B mRNA rather than the actual CK-B mRNA 3'UTR.

Furthermore, the soluble protein inhibitions is due to the reaction of the U937 cells to the short RNA sequences with the 3’UTR.

The introduction of these sequences(shot segement of RNA) into the U937D cells leads to CK-B synthesis. This makes 3’UTR sequences to bind to the translational repressor proteins, thus preventing them from binding to the CK-B mRNA .

COMPLETED QUE.

A common feature of many eukaryotic mRNAS is the presence of a rather long 3' UTR, which often contains consensus sequences. Creatine kinase B (CK-B) is an enzyme important in cellular metabolism. Certain cells—termed U937D cells—have lots of CK-B mRNA, but no CK- B enzyme is present. In these cells the 5’ end of the CK-B mRNA is bound to ribosomes, the mRNA is apparently not translated. Something inhibits the translation of the CK-B mRNA in these cells. Researchers introduced numerous short segments of RNA containing only 3’UTR sequences into U937D cells. As result, the U937D cells began to synthesize the CK-B enzyme, but the total amount of CK-B mRNA did not increase. The introduction of short segments of other RNA sequences did not stimulate the synthesis of CK-B; only the 3’UTR sequences turned on the translation of the enzyme. Based on these results, purpose a mechanism for how CK-B translation is inhibited in U937D cells. Explain how the introduction of short segments of RNA containing the 3'UTR sequences might remove the inhibition.

Explanation: