Schizosaccharomyces pombe Pmf1p is structurally and functionally related to Mmf1p of Saccharomyces cerevisiae

A novel family of small proteins, termed p14.5 or YERO57c/YJGFc, has been identified.Independent studies indicate that p14.5 family members are multifunctional proteinsinvolved in several pathways, e.g. regulation of translation or activation of the proteasem-calpain. We have previously shown that Mmf1p, a p14.5 of the budding yeastSaccharomyces cerevisiae, is localized in the mitochondria and influences mitochondrialDNA stability. In addition, we have demonstrated that Mmf1p is functionally related top14.5 of mammalian cells. To explore further the evolutionary conservation of themitochondrial function(s) of the p14.5s we have extended our study to the fission yeast,Schizosaccharomyces pombe. In this organism two p14.5 homologous proteins are present:Pmf1p (pombe mitochondrial factor 1) and Hpm1p (homologous Pmf1p factor 1). We havegenerated a specific Pmf1p antibody, which recognizes a single band of approximately15 kDa in total cellular extracts. Cellular fractionation experiments indicate that Pmf1plocalizes in the mitochondria as well as in the cytoplasm. We also show that Pmf1p sharesseveral properties of S. cerevisiae Mmf1p. Indeed, Pmf1p restores the wild-type phenotypewhen expressed in Dmmf1 S. cerevisiae cells. Deletion of the leader sequence of Pmf1pabrogates its ability to localize in mitochondria and to functionally replace Mmf1p. Thus,these data together with our previous study show that the mitochondrial function(s) of thep14.5 family members are highly conserved in eukaryotic cells.