Intracellular signaling from the endoplasmic reticulum to the nucleus

Cells respond to an accumulation of unfolded proteins in the endoplasmic re ticulum (ER) by increasing transcription of genes encoding ER resident prot eins. The information is transmitted from the ER lumen to the nucleus by an intracellular signaling pathway called the unfolded protein response (UPR) . Recent work has shown that this signaling pathway utilizes several novel mechanisms, including translational attenuation and a regulated mRNA splici ng step. In this review we aim to integrate these recent advances with curr ent knowledge about maintenance of ER composition and abundance.