Structural basis for cisplatin DNA damage tolerance by human polymerase η during cancer chemotherapy

Abstract

A major clinical problem in the use of cisplatin to treat cancers is tumor resistance. DNA polymerase η (Polη) is a key polymerase that allows cancer cells to cope with cisplatin–DNA adducts formed during chemotherapy. We present here a structure of human Polη inserting dCTP opposite a cisplatin intrastrand cross-link (PtGpG). We show that specificity of human Polη for PtGpG derives from an active site that is open to permit Watson-Crick geometry of the nascent PtGpG•dCTP base pair and to accommodate the lesion without steric hindrance. The specificity is augmented by residues Gln38 and Ser62 that interact with PtGpG, and Arg61 that interacts with incoming dCTP. Collectively, the structure provides a basis for understanding how Polη in human cells can tolerate DNA damage caused by cisplatin chemotherapy and offers a framework for the design of inhibitors in cancer therapy.

Stabilization of histone demethylase PHF8 by USP7 promotes breast carcinogenesis

“…It is tempting to speculate that the role of PHF8 in DDR might represent a novel, previously unappreciated contributing factor in the development of fragile X syndrome, the understanding of which will broaden the insight into the regulation of genome/epigenome integrity and the pathogenesis of neurological diseases. Moreover, chemo-and radiotherapy are designed to eliminate cancer cells through inducing DNA damage beyond repair by DDR machinery (63). However, cancerous cells often carry abnormalities in DDR machinery, rendering these cells resistant to DNA damage-based therapy (64).…”

Mechanism of somatic hypermutation at the WA motif by human DNA polymerase η

“…These structures revealed a uniquely enlarged active site that can readily accommodate two normal template bases, a cis-syn thymine dimer (CPD), or to a certain extent intrastrand cisplatin cross-linked guanines (Pt-GG). In addition, the "molecular splint" of human Pol η stabilizes the upstream DNA duplex in a normal B-form conformation, even in the presence of cross-linked bases by forming numerous salt bridges and hydrogen bonds with the phosphate backbones, thus facilitating primer extension after CPD lesions (24)(25)(26)(27). Misincorporation by Pol η, however, has not been investigated in a sequence-dependent manner or at atomic resolution.…”

“…Crystal structures of the polymerase domain of human Pol η (1-432 aa) complexed with different lesion DNA substrates were reported recently (24)(25)(26)(27). These structures revealed a uniquely enlarged active site that can readily accommodate two normal template bases, a cis-syn thymine dimer (CPD), or to a certain extent intrastrand cisplatin cross-linked guanines (Pt-GG).…”

“…To elucidate the molecular mechanism of Pol η in SHM, we set out to determine crystal structures of the polymerase domain of human Pol η (1-432 aa) (24)(25)(26)(27) in the process of misincorporating dGTP opposite T in the WA motif (TA or AA) and non-WA sequences (CA or GA) as well as when extending the primer after a T:G mispair. In addition, steady-state kinetic parameters are measured to complement structural observations.…”

Inhibition of Translesion DNA Synthesis as a Novel Therapeutic Strategy to Treat Brain Cancer

“…These include the high-fidelity polymerases, pol delta and pol epsilon, that are involved in chromosomal replication as well as pol eta and pol iota, which are specialized DNA polymerases that can efficiently replicate DNA lesions to produce drug resistance (30,31). Figure 2C provides Michaelis-Menten plots for the utilization of 5-NITP by all four DNA polymerases during the replication of an abasic site.…”