Role of the membrane-tethering region of Tyw1 in the activation of the iron regulon. A, shown is the sequence of the first 199 amino acids (AA) of Tyw1. TM denotes the transmembrane region, and repetitive amino acids are shown in boldface. B, shown is the immunofluorescence of cells transfected with Tyw1-His6-containing constructs visualized using an anti-His6 antibody and an antibody to the ER marker Dpm1. C, wild-type cells were transformed with plasmids expressing amino acids 1–199, 9–199, 29–199, 1–65, or 63–199 and a FET3-lacZ construct. Cells were assayed for β-galactosidase activity and cell protein (left panel). The right panel shows a Western blot of protein levels in transformed cells. D, shown is the immunofluorescence of cells transformed with constructs expressing different truncations of Tyw1-His6 and stained for His6 and Dpm1.