Protein kinase A inhibits tumor mutator APOBEC3B through phosphorylation
Protein kinase A inhibits tumor mutator APOBEC3B through phosphorylation
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DOI：
10.1038/s41598-019-44407-9
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发表时间：
2019-06-05
影响因子：
4.6
通讯作者：
Takaori-Kondo, Akifumi
中科院分区：
文献类型：
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作者：
Matsumoto, Tadahiko;Shirakawa, Kotaro;Takaori-Kondo, Akifumi
APOBEC3B胞苷脱氨酶(A3B)催化胞嘧啶在单链DNA中转化为尿嘧啶，并诱导各种类型肿瘤基因组DNA的C-to-T突变。APOBEC标志性突变的积累与乳腺癌或多发性骨髓瘤患者的预后不良相关，提示A3B活性可能是这些肿瘤中不利的DNA突变和克隆进化的原因。其他胞苷脱氨酶的保守苏氨酸残基的磷酸化，激活诱导脱氨酶(AID)和APOBEC3G，抑制它们的活性。在这里，我们展示了蛋白激酶A(PKA)与A3B物理结合并磷酸化Thr214。体外脱氨酶试验和外源DNA编辑试验证实，拟磷脂酶A3B突变体T214D和T214E完全失去脱氨酶活性。A3B磷酸化的分子动力学模拟表明，Thr214磷酸化破坏了磷酸化A3B催化核心与单链DNA之间的结合。这些突变体仍然至少部分地抑制逆转录病毒的感染性，并且还保留了全部的抗逆转录转座活性。这些结果表明，PKA介导的磷酸化抑制了A3B的诱变活性，而不破坏其固有免疫功能。因此，激活PKA可以减少A3B过表达肿瘤中突变的进一步积累。
APOBEC3B cytidine deaminase (A3B) catalyzes cytosine into uracil in single-strand DNA and induces C-to-T mutations in genomic DNA of various types of tumors. Accumulation of APOBEC signature mutations is correlated with a worse prognosis for patients with breast cancer or multiple myeloma, suggesting that A3B activity might be a cause of the unfavorable DNA mutations and clonal evolution in these tumors. Phosphorylation of conserved threonine residues of other cytidine deaminases, activation induced deaminase (AID) and APOBEC3G, inhibits their activity. Here we show that protein kinase A (PKA) physically binds to A3B and phosphorylates Thr214. In vitro deaminase assays and foreign DNA editing assays in cells confirm that phosphomimetic A3B mutants, T214D and T214E, completely lose deaminase activity. Molecular dynamics simulation of A3B phosphorylation reveals that Thr214 phosphorylation disrupts binding between the phospho-A3B catalytic core and ssDNA. These mutants still inhibit retroviral infectivity at least partially, and also retain full anti-retrotransposition activity. These results imply that PKA-mediated phosphorylation inhibits A3B mutagenic activity without destructing its innate immune functions. Therefore, PKA activation could reduce further accumulation of mutations in A3B overexpressing tumors.