Human REV3 DNA Polymerase Zeta Localizes to Mitochondria and Protects the Mitochondrial Genome.

Bhupendra Singh,Ayyasamy Vanniarajan,Keshav K Singh,Ping Liang,Xiurong Li,Kjerstin M Owens,Janine Santos

doi:10.1371/journal.pone.0140409

Abstract

To date, mitochondrial DNA polymerase γ (POLG) is the only polymerase known to be present in mammalian mitochondria. A dogma in the mitochondria field is that there is no other polymerase present in the mitochondria of mammalian cells. Here we demonstrate localization of REV3 DNA polymerase in the mammalian mitochondria. We demonstrate localization of REV3 in the mitochondria of mammalian tissue as well as cell lines. REV3 associates with POLG and mitochondrial DNA and protects the mitochondrial genome from DNA damage. Inactivation of Rev3 leads to reduced mitochondrial membrane potential, reduced OXPHOS activity, and increased glucose consumption. Conversely, inhibition of the OXPHOS increases expression of Rev3. Rev3 expression is increased in human primary breast tumors and breast cancer cell lines. Inactivation of Rev3 decreases cell migration and invasion, and localization of Rev3 in mitochondria increases survival and the invasive potential of cancer cells. Taken together, we demonstrate that REV3 functions in mammalian mitochondria and that mitochondrial REV3 is associated with the tumorigenic potential of cells.

Highlights

Mitochondria are involved in energy metabolism, cell proliferation, cell growth, apoptosis, and other cellular regulatory mechanisms
Using MitoProt II software, we have identified, at the N-terminal region of the human REV3 protein, a mitochondrial localization signal (MLS) that facilitates translocation of this protein to mitochondria
Translation initiation from the first AUG synthesizes a long isoform of REV3 (3130 amino acid; ~352kDa; NP_002903.3), and initiation from the second AUG generates a small isoform of REV3 (3052 amino acid; ~343kDa; AAG09402.1)

Summary

Introduction

Mitochondria are involved in energy metabolism, cell proliferation, cell growth, apoptosis, and other cellular regulatory mechanisms. Mitochondria contain their own DNA, which encodes 13 essential components of the respiratory chain and is replicated continuously in dividing cells and in postmitotic tissues. Failure to preserve the genetic integrity of the mitochondrial genome during replication results in depletion, deletion, or mutation of mitochondrial DNA (mtDNA), which impairs oxidative phosphorylation (OXPHOS) and causes cellular dysfunctions and diseases [1,2,3,4]. Mitochondrial DNA polymerase γ (POLG), the only polymerase. Mutations in Polg are associated with depletion of mtDNA, mitochondrial malfunction, aging, carcinogenesis, and various other diseases [7,8]. The mechanisms by which mitochondria ensure stability and integrity of their own genome remain to be elucidated

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Conclusion