@article{oai:repo.qst.go.jp:00079626,
 author = {Tsuda, Masataka and Kitamasu, Kaito and Kumagai, Chiho and Sugiyama, Kazuya and Nakano, Toshiaki and Ide, Hiroshi and Nakano, Toshiaki},
 journal = {DNA repair},
 month = {Mar},
 note = {Topoisomerase I (TOP1) is a pivotal enzyme that resolves DNA topological problems during replication and transcription. It forms an intermediate involving transient TOP1 DNA-protein crosslinks, known as the TOP1 cleavage complex (TOP1cc). Camptothecin, a frontline anticancer agent, freezes the reaction intermediate and generates irreversible TOP1ccs, which are 3ʹ -blocking lesions. It is widely accepted that TOP1cc is repaired via the two-step pathway. The first step involves the proteolytic degradation of TOP1cc to the crosslinked peptide by the proteasome. The second step involves the removal of the TOP1cc-derived peptide from DNA by Tyrosyl-DNA phosphodiesterase 1 (TDP1). In the present study, we developed a new assay system that measures the repair kinetics of TOP1cc in the first and second steps separately, using two monoclonal antibodies specific for the TOP1 protein and the TOP1catalytic site peptide that was crosslinked to DNA. This assay revealed that although TDP1-deficient (TDP1-/-) TK6 cells were normal in the kinetics of the first step, did a delay in the kinetics of the second step relative to wild-type cells. It has been reported that Tyrosyl-DNA phosphodiesterase 2 (TDP2) promotes the repair of TOP1-induced DNA damage when TDP1 is absent in cells. Using the new assay system, we also demonstrated that TDP2 promoted the second, but not the first, step of TOP1cc repair when TDP1 is absent in cells. Finally, we analyzed the sensitivities of TK6 cells deficient in TDP1 and/or TDP2 to agents that produce 3ʹ -blocking lesions. TDP1-/-TDP2-/- cells were more sensitive than TDP1-/- or TDP2-/- cells to cytarabine, abacavir, azidothymidine (zidovudine), gemcitabine, and trifluridine. Taken together, our findings reveal a broad involvement of TDP2 in the repair of 3ʹ-blocking lesions.},
 pages = {102837--10248},
 title = {Tyrosyl-DNA phosphodiesterase 2 (TDP2) repairs topoisomerase 1 DNA-protein crosslinks and 3ʹ-blocking lesions in the absence of tyrosyl-DNA phosphodiesterase 1 (TDP1)},
 volume = {89},
 year = {2020}
}