Keratinocyte differentiation induces APOBEC3A, 3B, and mitochondrial DNA hypermutation

Kousho Wakae,Lusheng Que,Mitsuhiro Nakamura,Tomoaki Nishiyama,Satoru Kondo,Cong Chen,Kina Kase,Masamichi Muramatsu,Zhe Wang,Kouichi Kitamura,Tomomi Nakahara,Hiroshi Fujiwara,Tohru Kiyono,Md Mohiuddin,Kazuyoshi Hosomochi,Takashi Izuka,Atsushi Tajima,Tomokazu Yoshizaki,Md Monjurul Ahasan

doi:10.1038/s41598-018-27930-z

Abstract

Mitochondrial DNA (mtDNA) mutations are found in many types of cancers and suspected to be involved in carcinogenesis, although the mechanism has not been elucidated. In this study, we report that consecutive C-to-T mutations (hypermutations), a unique feature of mutations induced by APOBECs, are found in mtDNA from cervical dysplasia and oropharyngeal cancers. In vitro, we found that APOBEC3A (A3A) and 3B (A3B) expression, as well as mtDNA hypermutation, were induced in a cervical dysplastic cell line W12 when cultured in a differentiating condition. The ectopic expression of A3A or A3B was sufficient to hypermutate mtDNA. Fractionation of W12 cell lysates and immunocytochemical analysis revealed that A3A and A3B could be contained in mitochondrion. These results suggest that mtDNA hypermutation is induced upon keratinocyte differentiation, and shed light on its molecular mechanism, which involves A3s. The possible involvement of mtDNA hypermutations in carcinogenesis is also discussed.

Highlights

Mitochondrial DNA mutations are found in many types of cancers and suspected to be involved in carcinogenesis, the mechanism has not been elucidated
It has been reported that Mitochondrial DNA (mtDNA) was mutated in many types of cancers, including cervical cancer (CC) and OPC13,25,26
We demonstrated using 3D-PCR and next-generation sequencing (NGS) that cells from cervical intraepithelial neoplasia (CIN) and oropharyngeal cancer (OPC) specimens contained hypermutated mtDNA, that correlated with A3B expression (Figs 1 and 2, and Supplementary Figs S1 and S2)

Summary

Introduction

Mitochondrial DNA (mtDNA) mutations are found in many types of cancers and suspected to be involved in carcinogenesis, the mechanism has not been elucidated. (b,c) Mutation matrices (b) and dinucleotide analysis (c) of the hypermutated reads, obtained from D-loop–ND1 and ND5–tRNA-F, amplified from CIN sample (c) Total DNAs were subjected to 3D-PCR targeting COI, along with plasmid controls containing amplicons with 0, 17, and 30 C-to-T mutations.

Results

Conclusion