Repair of topoisomerase 1–induced DNA damage by tyrosyl-DNA phosphodiesterase 2 (TDP2) is dependent on its magnesium binding
Naoto Shimizu, Yusaku Hamada, Ryosuke Morozumi, Junpei Yamamoto, Shigenori Iwai, Kei‐ichi Sugiyama, Hiroshi Ide, Masataka Tsuda
Abstract
Topoisomerases are enzymes that relax DNA supercoiling during replication and transcription. Camptothecin, a topoisomerase 1 (TOP1) inhibitor, and its analogs trap TOP1 at the 3′ end of DNA as a DNA-bound intermediate, resulting in DNA damage that can kill cells. Drugs with this mechanism of action are widely used to treat cancers. It has previously been shown that tyrosyl-DNA phosphodiesterase 1 (TDP1) repairs TOP1-induced DNA damage induced by camptothecin. In addition, tyrosyl-DNA phosphodiesterase 2 (TDP2) plays critical roles in repairing topoisomerase 2 (TOP2)-induced DNA damage at the 5′ end of DNA and in promoting the repair of TOP1-induced DNA damage in the absence of TDP1. However, the catalytic mechanism by which TDP2 processes TOP1-induced DNA damage has not been elucidated. In this study, we found that a similar catalytic mechanism underlies the repair of TOP1- and TOP2-induced DNA damage by TDP2, with Mg 2+ –TDP2 binding playing a role in both repair mechanisms. We show chain-terminating nucleoside analogs (CTNAs) are incorporated into DNA at the 3′ end and abort DNA replication to kill cells. Furthermore, we found that Mg 2+ –TDP2 binding also contributes to the repair of incorporated CTNAs. Overall, these findings reveal the role played by Mg 2+ –TDP2 binding in the repair of both 3′- and 5′-blocking DNA damage.