Pet127p, a Membrane-Associated Protein Involved in Stability and Processing of Saccharomyces cerevisiae Mitochondrial RNAs

Abstract

Nuclear mutations that inactivate the Saccharomyces cerevisiae gene PET127 dramatically increased the levels of mutant COX3 and COX2 mitochondrial mRNAs that were destabilized by mutations in their 5′ untranslated leaders. The stabilizing effect of pet127∆ mutations occurred both in the presence and in the absence of translation. In addition, pet127∆ mutations had pleiotropic effects on the stability and 5′ end processing of some wild-type mRNAs and the 15S rRNA but produced only a leaky nonrespiratory phenotype at 37 °C. Overexpression of PET127 completely blocked respiratory growth and caused cells to lose wild-type mitochondrial DNA, suggesting that too much Pet127p prevents mitochondrial gene expression. Epitope-tagged Pet127p was specifically located in mitochondria and associated with membranes. These findings suggest that Pet127p plays a role in RNA surveillance and/or RNA processing and that these functions may be membrane bound in yeast mitochondria.