PMID: 30709915
Ouzon-Shubeita H, Baker M, Koag MC, Lee S
Structural basis for the bypass of the major oxaliplatin-DNA adducts by human DNA polymerase eta.
Biochem J. 2019 Feb 1. pii: BCJ20180848. doi: 10.1042/BCJ20180848.
Oxaliplatin, together with cisplatin, is among the most important drugs used in cancer chemotherapy. Oxaliplatin, which contains a bulky diaminocyclohexane (DACH) moiety, kills cancer cells mainly by producing (DACH)Pt-GpG intrastrand cross-links that impede transcription. The Pt-GpG tolerance by translesion DNA synthesis (TLS) polymerases contributes to the resistance of tumors to platinum-based chemotherapy. In particular, human DNA polymerase eta (Poleta) readily bypasses Pt-GpG adducts. While many structural studies have addressed how TLS polymerases interact with cisplatin-DNA adducts, a structure of DNA polymerase in complex with oxaliplatin-DNA adducts has not been reported, limiting our understanding of bypass of the bulky (DACH)Pt-GpG lesion by TLS polymerases. Herein, we report the first structure of DNA polymerase bound to oxaliplatinated DNA. We determined a crystal structure of Poleta incorporating dCTP opposite the 3'G of the (DACH)Pt-GpG, which provides insights into accurate, efficient bypass of the oxaliplatin-GpG adducts by TLS polymerases. In the catalytic site of Poleta, the 3'G of the (DACH)Pt-GpG formed three Watson-Crick hydrogen bonds with incoming dCTP and the primer terminus 3'-OH was optimally positioned for nucleotidyl transfer. To accommodate the bulky (DACH)Pt-GpG lesion, the Val59-Trp64 loop in the finger domain of Poleta shifted from the positions observed in the corresponding Poleta-cisplatin-GpG and undamaged structures, suggesting that the flexibility of the Val59-Trp64 loop allows the enzyme's bypass of the (DACH)Pt-GpG adducts. Overall, the Poleta-oxaliplatin-GpG structure provides structural basis for TLS-mediated bypass of the major oxaliplatin-DNA adducts and insights into resistance to platinum-based chemotherapy in humans.