Yeast expression of mammalian Onzin and fungal FCR1 suggests ancestral functions of PLAC8 proteins in mitochondrial metabolism and DNA repair

Stefania Daghino,Silvia Perotto,Luigi Di Vietro,Luca Petiti,Elena Martino,Tiziana Lodi,Cristina Dallabona

doi:10.1038/s41598-019-43136-3

Abstract

The cysteine-rich PLAC8 domain of unknown function occurs in proteins found in most Eukaryotes. PLAC8-proteins play important yet diverse roles in different organisms, such as control of cell proliferation in animals and plants or heavy metal resistance in plants and fungi. Mammalian Onzin can be either pro-proliferative or pro-apoptotic, depending on the cell type, whereas fungal FCR1 confers cadmium tolerance. Despite their different role in different organisms, we hypothesized common ancestral functions linked to the PLAC8 domain. To address this hypothesis, and to investigate the molecular function of the PLAC8 domain, murine Onzin and fungal FCR1 were expressed in the PLAC8-free yeast Saccharomyces cerevisiae. The two PLAC8-proteins localized in the nucleus and induced almost identical phenotypes and transcriptional changes when exposed to cadmium stress. Like FCR1, Onzin also reduced DNA damage and increased cadmium tolerance by a DUN1-dependent pathway. Both proteins activated transcription of ancient mitochondrial pathways such as leucine and Fe-S cluster biosynthesis, known to regulate cell proliferation and DNA repair in yeast. These results strongly suggest a common ancestral function of PLAC8 proteins and open new perspectives to understand the role of the PLAC8 domain in the cellular biology of Eukaryotes.

Highlights

The PLAC8 domain was described for the first time in the protein Onzin, the product of the human Placenta-Specific Gene 81
Www.nature.com/scientificreports genomes, the only PLAC8 genes characterized to date are two Fungal Cadmium Resistance (FCR) genes identified in a metal tolerant isolate of the mycorrhizal ascomycete Oidiodendron maius[19,20], which increased cadmium resistance when expressed in S. cerevisiae
PLAC8 proteins have likely evolved from a common ancestral protein and an intriguing question is whether, despite their very different roles in different organisms and cell types, a molecular function common to all biological systems can be ascribed to the PLAC8 domain

Summary

Introduction

The PLAC8 domain was described for the first time in the protein Onzin, the product of the human Placenta-Specific Gene 81. Spot dilution assays at two CdSO4 concentrations (Fig. 2a) showed that both Onzin and FCR1 confer cadmium tolerance to S. cerevisiae, when compared with the control strain transformed with the empty vector. Cells exposed to cadmium display a reduced DNA mutation rate when they express either FCR1 or Onzin, the relationship between these two PLAC8 proteins and the MMR complex remains unclear.

Results

Conclusion