TP53 codon 72 polymorphism affects accumulation of mtDNA damage in human cells

Serena Altilia,Giuseppe Passarino,Igor Boris Roninson,Gianluca Galazzo,Davide Malagoli,Claudio Franceschi,Giuseppina Rose,Catia Lanzarini,Paolina Crocco,Donald Carl Porter,Aurelia Santoro,Stefano Salvioli,Josué Adolfo Ballesteros Álvarez

doi:10.18632/aging.100425

Abstract

Human TP53 gene is characterised by a polymorphism at codon 72 leading to an Arginine-to-Proline (R/P) substitution. The two resulting p53 isoforms have a different subcellular localisation after stress (more nuclear or more mitochondrial for the P or R isoform, respectively). p53P72 variant is more efficient than p53R72 in inducing the expression of genes involved in nuclear DNA repair. Since p53 is involved also in mitochondrial DNA (mtDNA) maintenance, we wondered whether these p53 isoforms are associated with different accumulation of mtDNA damage. We observed that cells bearing p53R72 accumulate lower amount of mtDNA damage upon rotenone stress with respect to cells bearing p53P72, and that p53R72 co-localises with polymerase gamma more than p53P72. We also analysed the in vivo accumulation of heteroplasmy in a 300 bp fragment of mtDNA D-loop of 425 aged subjects. We observed that subjects with heteroplasmy higher than 5% are significantly less than expected in the p53R72/R72 group. On the whole, these data suggest that the polymorphism of TP53 at codon 72 affects the accumulation of mtDNA mutations, likely through the different ability of the two p53 isoforms to bind to polymerase gamma, and may contribute to in vivo accumulation of mtDNA mutations.

Highlights

Mitochondrial DNA is a small, doublestranded circular molecule of 16,569 bp that is contained in many copies inside mitochondria, packaged into multimeric complexes called nucleoids made up of proteins and nucleic acids [1]
Total www.impactaging.com Mitochondrial DNA (mtDNA) integrity tends to decrease with age, as demonstrated by the accumulation of point mutations and deletions in a variety of tissues during aging in humans, monkeys, and rodents [35,36]
The accumulation of somatic mtDNA mutations has likely a causative role in the aging of the organisms, as suggested by animal models such as the mutator mice lacking the proofreading activity of polymerase gamma [5,6,37]

Summary

INTRODUCTION

Mitochondrial DNA (mtDNA) is a small, doublestranded circular molecule of 16,569 bp that is contained in many copies inside mitochondria, packaged into multimeric complexes called nucleoids made up of proteins and nucleic acids [1]. Since as summarised above the two p53 isoforms have a different tendency to localise at mitochondria, we wondered whether they can differ in capability to maintain mtDNA stability, and whether this may occur through a differential binding to mtDNA replisome components such as polg. To check this hypothesis we performed in vitro as well as in vivo studies whose results suggest that this is the case

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS