Inhibition of ATR protein kinase activity by schisandrin B in DNA damage response

Abstract

ATM and ATR protein kinases play a crucial role in cellular DNA damage responses. The inhibition of ATM and ATR can lead to the abolition of the function of cell cycle checkpoints. In this regard, it is expected that checkpoint inhibitors can serve as sensitizing agents for anti-cancer chemo/radiotherapy. Although several ATM inhibitors have been reported, there are no ATR-specific inhibitors currently available. Here, we report the inhibitory effect of schisandrin B (SchB), an active ingredient of Fructus schisandrae, on ATR activity in DNA damage response. SchB treatment significantly decreased the viability of A549 adenocarcinoma cells after UV exposure. Importantly, SchB treatment inhibited both the phosphorylation levels of ATM and ATR substrates, as well as the activity of the G2/M checkpoint in UV-exposed cells. The protein kinase activity of immunoaffinity-purified ATR was dose-dependently decreased by SchB in vitro (IC50: 7.25 μM), but the inhibitory effect was not observed in ATM, Chk1, PI3K, DNA-PK, and mTOR. The extent of UV-induced phosphorylation of p53 and Chk1 was markedly reduced by SchB in ATM-deficient but not siATR-treated cells. Taken together, our demonstration of the ability of SchB to inhibit ATR protein kinase activity following DNA damage in cells has clinical implications in anti-cancer therapy.

DNA Damage Induced by Ultrasound and Cellular Responses

“…In general, ATM preferentially phosphorylates Chk2 at Thr68 over Chk1 at Ser345, and Chk1 phosphorylation is largely dependent on ATR [39]. Consistent with previous reports, US-induced Chk1 phosphorylation was attenuated by selective inhibitors against ATR (described in [40]), but not ATM inhibitors. Chk1 inhibition using the selective inhibitor SB218078, or Chk1-targeted siRNA transfection, decreased the population of cells in the G 2 /M phase and increased that in SubG 1 phase following US-exposure, indicating that Chk1 plays an essential role in the G 2 /M arrest and cell survival in response to US-induced DNA damage.…”

Coronavirus Infection Induces DNA Replication Stress Partly through Interaction of Its Nonstructural Protein 13 with the p125 Subunit of DNA Polymerase δ

“…3, a and b). During the course of this study, SchB, a dibenzocyclooctadiene derivative isolated from Fructus Schisandrae, was reported to be a specific ATR inhibitor (63). Similar to CGK733 and caffeine, the addition of 10 -20 M SchB to IBV-infected H1299 cells either pre-or post-infection showed potent inhibition of IBV replication (Fig.…”

Chemical inhibition of DNA repair kinases as a promising tool in oncology

“…This is in contrast to combined treatment with UV-radiation, which caused the G 2 /M checkpoint abrogation and the decrease in phosphorylations of p53 (Ser 15) and CHK1 (Ser 317). Importantly, this was observed in ATM-deficient cells but not cells with ATR depleted by siRNA 82 . Schisandrin B also potentiated the effect of doxorubicin 84 .…”

“…It also caused synthetic death in combination with the PARP inhibitor or in XRCC1-defective cells 79 . 81,82 ). This inhibitor is a mixture of gomisin N and γ-schisandrin which are the diastereomers of each other.…”