AU-rich elements in mRNA influence stability by promoting what?

• A. They stabilize mRNA by preventing decay.
• B. They promote degradation and reduce mRNA half-life.
• C. They are located only in coding regions and do not affect stability.
• D. They enhance translation efficiency.

Answer: (B)

AU-rich elements signal rapid mRNA turnover by promoting degradation, shortening the mRNA’s half-life. These sequences, usually in the 3' untranslated region, recruit ARE-binding proteins that stimulate deadenylation of the poly(A) tail. Once the tail is shortened, the mRNA becomes more susceptible to decapping and exonucleolytic decay, leading to faster breakdown. This mechanism lets cells rapidly dial down expression of many regulated transcripts, such as cytokines. While some ARE-binding proteins can affect translation in certain contexts, the dominant effect of AU-rich elements on stability is to promote degradation rather than stabilization, and they are not typically located in coding regions.