Role of tyrosyl-DNA phosphodiesterase (TDP1) in mitochondria

Abstract

Human tyrosyl-DNA phosphodiesterase (TDP1) hydrolyzes the phosphodiester bond at a DNA 3′-end linked to a tyrosyl moiety and has been implicated in the repair of topoisomerase I (Top1)-DNA covalent complexes. TDP1 can also hydrolyze other 3′-end DNA alterations including 3′-phosphoglycolate and 3′-abasic sites, and exhibits 3′-nucleosidase activity indicating it may function as a general 3′-end-processing DNA repair enzyme. Here, using laser confocal microscopy, subcellular fractionation and biochemical analyses we demonstrate that a fraction of the TDP1 encoded by the nuclear TDP1 gene localizes to mitochondria. We also show that mitochondrial base excision repair depends on TDP1 activity and provide evidence that TDP1 is required for efficient repair of oxidative damage in mitochondrial DNA. Together, our findings provide evidence for TDP1 as a novel mitochondrial enzyme.DNA repair | ligase III | oxidative DNA damage | topoisomerase I | mitochondrial BER

Tyrosyl-DNA Phosphodiesterase 1 (TDP1) Repairs DNA Damage Induced by Topoisomerases I and II and Base Alkylation in Vertebrate Cells

“…Tdp1Ϫ/Ϫ cells showed consistent hypersensitivity to etoposide, a selective Top2 inhibitor (3,46), marginal sensitivity to IR, and strong sensitivity to bleomycin in agreement with the fact that both IR and bleomycin induce DSBs and/or single strand breaks with 3Ј-PG ends that can be processed by Tdp1 (6,37,39,54). Tdp1Ϫ/Ϫ cells also showed significant sensitivity to MMS and mild sensitivity to H 2 O 2 .…”

“…Supernatants were collected, aliquoted, and stored at Ϫ80°C. Preparation of mitochondrial and nuclear extracts was performed as described (6). Lysates were prepared in the same manner as whole cell lysates.…”

“…Spinocerebellar ataxia neuropathy 1 lymphoblastoid cells, Tdp1 knock-out mice, and murine cells derived from these mice all exhibit hypersensitivity to CPT (20, 21, 30 -36). The recent finding that Tdp1 localizes to mitochondria and contributes to efficient repair of oxidative damage in mitochondrial DNA revealed a novel role for Tdp1 in mitochondrial DNA repair (6 In addition to 3Ј-phosphotyrosyl bonds, Tdp1 hydrolyzes other adducts that block DNA ends, including 3Ј-phosphoglycolates (3Ј-PGs) (37) and AP sites (19,38) albeit less effectively (18,39). Endogenous oxidative damage or anticancer treatments (i.e.…”

“…To untwist the DNA, Top1 nicks one DNA strand by covalently linking its catalytic tyrosine residue to a 3Ј-phosphate, which allows the controlled rotation of the broken strand around the intact strand (4,5). Once supercoiling is removed, Top1 is released by religation of the DNA 3Ј-phosphate with the 5Ј-hydroxyl end (2,6). Camptothecin (CPT) derivatives, such as topotecan and irinotecan, are Top1 inhibitors widely used in cancer chemotherapy (7).…”

Neuroprotection and repair of 3′-blocking DNA ends by glaikit (gkt) encoding Drosophila tyrosyl-DNA phosphodiesterase 1 (TDP1)

“…To ligate and extend the ends of broken DNA, the modified 3′ end must be removed. Tyrosyl-DNA phosphodiesterase (TDP1), first identified in yeast, catalyzes the hydrolysis of 3′-phosphotyrosyl, 3′-phosphoglycolate, and 3′-nucleoside bonds (8,(10)(11)(12)(13)(14). The irreversible Top1-DNA complexes and 3′-blocking nucleoside lesions are cleaved by TDP1, leaving 3′-terminal phosphates, which are further processed by polynucleotide kinase phosphatase before ligation and/or extension by polymerases.…”