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EMBO Rep. 2018 Feb 9. pii: e42139. doi: 10.15252/embr.201642139. [Epub ahead of print]

Mitochondrial tyrosyl-DNA phosphodiesterase 2 and its TDP2S short isoform.

Author information

1
Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA shar-yin.huang@nih.gov pommier@nih.gov.
2
Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA.
3
Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
4
Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA.
5
Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada.

Abstract

Tyrosyl-DNA phosphodiesterase 2 (TDP2) repairs abortive topoisomerase II cleavage complexes. Here, we identify a novel short isoform of TDP2 (TDP2S) expressed from an alternative transcription start site. TDP2S contains a mitochondrial targeting sequence, contributing to its enrichment in the mitochondria and cytosol, while full-length TDP2 contains a nuclear localization signal and the ubiquitin-associated domain in the N-terminus. Our study reveals that both TDP2 isoforms are present and active in the mitochondria. Comparison of isogenic wild-type (WT) and TDP2 knockout (TDP2-/-/-) DT40 cells shows that TDP2-/-/- cells are hypersensitive to mitochondrial-targeted doxorubicin (mtDox), and that complementing TDP2-/-/- cells with human TDP2 restores resistance to mtDox. Furthermore, mtDox selectively depletes mitochondrial DNA in TDP2-/-/- cells. Using CRISPR-engineered human cells expressing only the TDP2S isoform, we show that TDP2S also protects human cells against mtDox. Finally, lack of TDP2 in the mitochondria reduces the mitochondria transcription levels in two different human cell lines. In addition to identifying a novel TDP2S isoform, our report demonstrates the presence and importance of both TDP2 isoforms in the mitochondria.

KEYWORDS:

DNA repair; mitochondria; mitochondrial DNA; topoisomerase

PMID:
29438979
DOI:
10.15252/embr.201642139
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