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The mitochondrial type IB topoisomerase drives mitochondrial translation and carcinogenesis.

ABSTRACT: Mitochondrial topoisomerase IB (TOP1MT) is a nuclear-encoded topoisomerase, exclusively localized to mitochondria, which resolves topological stress generated during mtDNA replication and transcription. Here, we report that TOP1MT is overexpressed in cancer tissues and demonstrate that TOP1MT deficiency attenuates tumor growth in human and mouse models of colon and liver cancer. Due to their mitochondrial dysfunction, TOP1MT-KO cells become addicted to glycolysis, which limits synthetic building blocks and energy supply required for the proliferation of cancer cells in a nutrient-deprived tumor microenvironment. Mechanistically, we show that TOP1MT associates with mitoribosomal subunits, ensuring optimal mitochondrial translation and assembly of oxidative phosphorylation complexes that are critical for sustaining tumor growth. The TOP1MT genomic signature profile, based on Top1mt-KO liver cancers, is correlated with enhanced survival of hepatocellular carcinoma patients. Our results highlight the importance of TOP1MT for tumor development, providing a potential rationale to develop TOP1MT-targeted drugs as anticancer therapies.

SUBMITTER: Baechler SA

PROVIDER: S-EPMC6325124 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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The mitochondrial type IB topoisomerase drives mitochondrial translation and carcinogenesis.

Baechler S A SA Factor V M VM Dalla Rosa I I Ravji A A Becker D D Khiati S S Miller Jenkins L M LM Lang M M Sourbier C C Michaels S A SA Neckers L M LM Zhang H L HL Spinazzola A A Huang S N SN Marquardt J U JU Pommier Y Y

Nature communications 20190108 1

Mitochondrial topoisomerase IB (TOP1MT) is a nuclear-encoded topoisomerase, exclusively localized to mitochondria, which resolves topological stress generated during mtDNA replication and transcription. Here, we report that TOP1MT is overexpressed in cancer tissues and demonstrate that TOP1MT deficiency attenuates tumor growth in human and mouse models of colon and liver cancer. Due to their mitochondrial dysfunction, TOP1MT-KO cells become addicted to glycolysis, which limits synthetic building ...[more]

PMID: 30622257

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Project description:Type IB topoisomerases unwind positive and negative DNA supercoils and play a key role in removing supercoils that would otherwise accumulate at replication and transcription forks. An interesting question is whether topoisomerase activity is regulated by the topological state of the DNA, thereby providing a mechanism for targeting the enzyme to highly supercoiled DNA domains in genomes. The type IB enzyme from variola virus (vTopo) has proven to be useful in addressing mechanistic questions about topoisomerase function because it forms a reversible 3'-phosphotyrosyl adduct with the DNA backbone at a specific target sequence (5'-CCCTT-3') from which DNA unwinding can proceed. We have synthesized supercoiled DNA minicircles (MCs) containing a single vTopo target site that provides highly defined substrates for exploring the effects of supercoil density on DNA binding, strand cleavage and ligation, and unwinding. We observed no topological dependence for binding of vTopo to these supercoiled MC DNAs, indicating that affinity-based targeting to supercoiled DNA regions by vTopo is unlikely. Similarly, the cleavage and religation rates of the MCs were not topologically dependent, but topoisomers with low superhelical densities were found to unwind more slowly than highly supercoiled topoisomers, suggesting that reduced torque at low superhelical densities leads to an increased number of cycles of cleavage and ligation before a successful unwinding event. The K271E charge reversal mutant has an impaired interaction with the rotating DNA segment that leads to an increase in the number of supercoils that were unwound per cleavage event. This result provides evidence that interactions of the enzyme with the rotating DNA segment can restrict the number of supercoils that are unwound. We infer that both superhelical density and transient contacts between vTopo and the rotating DNA determine the efficiency of supercoil unwinding. Such determinants are likely to be important in regulating the steady-state superhelical density of DNA domains in the cell.

Dataset Information

The mitochondrial type IB topoisomerase drives mitochondrial translation and carcinogenesis.

Publications

The mitochondrial type IB topoisomerase drives mitochondrial translation and carcinogenesis.

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