The unfolded protein response: an intracellular signalling pathway with many surprising features

The unfolded protein response (UPR) is an intracellular signalling pathway - originating in the endoplasmic reticulum (ER) and leaning to the cell nucleus - that controls transcription of genes encoding ER-resident proteins. Recent developments in this field show that this pathway utilizes unique regulatory mechanisms, including translational attenuation ann a regulated mRNA splicing step catalysed by a bifunctional transmembrane kinase/endoribonuclease ann tRNA ligase. This review describes the characterization of the UPR signalling pathway, focusing on the novel regulatory mechanisms that it has revealed.