THE HANSENULA-POLYMORPHA PER8 GENE ENCODES A NOVEL PEROXISOMAL INTEGRAL MEMBRANE-PROTEIN INVOLVED IN PROLIFERATION

We previously described the isolation of mutants of the methylotrophic yeast Hansenula polymorpha that are defective in peroxisome biogenesi s. Here, we describe the characterization of one of these mutants, per 8, and the cloning of the PER8 gene. In either methanol or methylamine medium, conditions that normally induce the organelles, per8 cells co ntain no peroxisome-like structures and peroxisomal enzymes are locate d in the cytosol. The sequence of PER8 predicts that its product (Per8 p) is a novel polypeptide of 34 kD, and antibodies against Per8p recog nize a protein of 31 kD. Analysis of the primary sequence of Per8p rev ealed a 39-amino-acid cysteine-rich segment with similarity to the C3H C4 family of zinc-finger motifs. Overexpression of PER8 results in a m arkedly enhanced increase in peroxisome numbers. We show that Per8p is an integral membrane protein of the peroxisome and that it is concent rated in the membranes of newly formed organelles. We propose that Per 8p is a component of the molecular machinery that controls the prolife ration of this organelle.