THE UNFOLDED PROTEIN RESPONSE COORDINATES THE PRODUCTION OF ENDOPLASMIC-RETICULUM PROTEIN AND ENDOPLASMIC-RETICULUM MEMBRANE

The endoplasmic reticulum (ER) is a multifunctional organelle responsi ble for production of both lumenal and membrane components of secretor y pathway compartments. Secretory proteins are folded, processed, and sorted in the ER lumen and lipid synthesis occurs on the ER membrane i tself. In the yeast Saccharomyces cerevisiae, synthesis of ER componen ts is highly regulated: the ER-resident proteins by the unfolded prote in response and membrane lipid synthesis by the inositol response. We demonstrate that these two responses are intimately linked, forming di fferent branches of the same pathway. Furthermore, we present evidence indicating that this coordinate regulation plays a role in ER biogene sis.