PDF(Pubmed)
Abstract：
DNA polymerase theta (Polθ) is a DNA helicase-polymerase protein that facilitates DNA repair and is synthetic lethal with homology-directed repair (HDR) factors. Thus, Polθ is a promising precision oncology drug-target in HDR-deficient cancers. Here, we characterize the binding and mechanism of action of a Polθ helicase (Polθ-hel) small-molecule inhibitor (AB25583) using cryo-EM. AB25583 exhibits 6 nM IC50 against Polθ-hel, selectively kills BRCA1/2-deficient cells, and acts synergistically with olaparib in cancer cells harboring pathogenic BRCA1/2 mutations. Cryo-EM uncovers predominantly dimeric Polθ-hel:AB25583 complex structures at 3.0-3.2 Å. The structures reveal a binding-pocket deep inside the helicase central-channel, which underscores the high specificity and potency of AB25583. The cryo-EM structures in conjunction with biochemical data indicate that AB25583 inhibits the ATPase activity of Polθ-hel helicase via an allosteric mechanism. These detailed structural data and insights about AB25583 inhibition pave the way for accelerating drug development targeting Polθ-hel in HDR-deficient cancers.
摘要：
DNA聚合酶theta（Polθ）是一种DNA解旋酶-聚合酶蛋白，可促进DNA修复，并且对同源定向修复（HDR）因子具有合成致死性。因此，Pole是HDR缺陷癌症中一种有前途的精准肿瘤药物靶标。这里,我们使用cryo-EM表征了Polθ解旋酶（Polθ-hel）小分子抑制剂（AB25583）的结合和作用机制。AB25583对Pole-hel,选择性杀死BRCA1/2缺陷细胞，并在携带致病性BRCA1/2突变的癌细胞中与奥拉帕尼协同作用。Cryo-EM在3.0-3.2µ上主要发现二聚体Polθ-hel：AB25583复杂结构。这些结构揭示了解旋酶中央通道深处的结合袋，这强调了AB25583的高特异性和效力。低温EM结构与生化数据的结合表明，AB25583通过变构机制抑制了Polθ-hel解旋酶的ATPase活性。这些关于AB25583抑制的详细结构数据和见解为加速HDR缺陷型癌症中靶向Pole-hel的药物开发铺平了道路。
