Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, Box 1677, 1425 Madison Avenue, New York, NY, 10029, USA.
Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77755-1061, USA.
Sci Rep. 2019 Nov 8;9(1):16400. doi: 10.1038/s41598-019-52703-7.
Cytarabine (AraC) is the mainstay chemotherapy for acute myeloid leukemia (AML). Whereas initial treatment with AraC is usually successful, most AML patients tend to relapse, and AraC treatment-induced mutagenesis may contribute to the development of chemo-resistant leukemic clones. We show here that whereas the high-fidelity replicative polymerase Polδ is blocked in the replication of AraC, the lower-fidelity translesion DNA synthesis (TLS) polymerase Polη is proficient, inserting both correct and incorrect nucleotides opposite a template AraC base. Furthermore, we present high-resolution crystal structures of human Polη with a template AraC residue positioned opposite correct (G) and incorrect (A) incoming deoxynucleotides. We show that Polη can accommodate local perturbation caused by the AraC via specific hydrogen bonding and maintain a reaction-ready active site alignment for insertion of both correct and incorrect incoming nucleotides. Taken together, the structures provide a novel basis for the ability of Polη to promote AraC induced mutagenesis in relapsed AML patients.
阿糖胞苷（AraC）是急性髓细胞白血病（AML）的主要化疗药物。虽然最初用 AraC 治疗通常是成功的，但大多数 AML 患者往往会复发，并且 AraC 治疗诱导的突变可能导致化疗耐药性白血病克隆的发展。我们在这里表明，高保真复制聚合酶 Polδ 在 AraC 的复制中被阻断，而低保真跨损伤 DNA 合成（TLS）聚合酶 Polη 则很有效，能够在模板 AraC 碱基的对面插入正确和错误的核苷酸。此外，我们呈现了人源 Polη 与模板 AraC 残基相对应的正确（G）和错误（A）入脱氧核苷酸的高分辨率晶体结构。我们表明，Polη 可以通过特定的氢键来适应由 AraC 引起的局部扰动，并保持反应准备好的活性位点对齐，以插入正确和错误的入核苷酸。总之，这些结构为 Polη 在复发的 AML 患者中促进 AraC 诱导的突变提供了新的基础。
