MicroRNAs in ER Stress: Divergent Roles in Cell Fate Decisions

MicroRNAs are small, noncoding RNAs which regulate protein expression post-transcriptionally. They respond to changes in a cell's environment and can promote cell death or cell survival depending on the context. Recent studies have linked microRNAs to the unfolded protein response pathway. This pathway is activated in the endoplasmic reticulum by conditions which interfere with the normal functions of the endoplasmic reticulum. The cell fate outcomes consequent to the activation of the unfolded protein response are binary, either cell survival or cell death. MicroRNAs can regulate multiple components of this pathway to tip the cell towards either fate. Inositol-requiring enzyme 1 alpha, a canonical unfolded protein response sensor and mediator, has inherent endoribonuclease activity. Interestingly, recently, it has been demonstrated that it can target microRNAs in addition to its previously known targets. This review highlights key papers in this rapidly emerging field.