Bromodomain and extra‐terminal (BET) family proteins, BRD2‐4 and T, are important drug targets; however, the biological functions of each bromodomain remain ill‐defined. Chemical probes that selectively inhibit a single BET bromodomain are lacking, although pan inhibitors of the first (D1), and second (D2), bromodomain are known. Here, we develop selective BET D1 inhibitors with preferred binding to BRD4 D1. In competitive inhibition assays, we show that our lead compound is 9–33 fold selective for BRD4 D1 over the other BET bromodomains. X‐ray crystallography supports a role for the selectivity based on reorganization of a non‐conserved lysine and displacement of an additional structured water in the BRD4 D1 binding site relative to our prior lead. Whereas pan‐D1 inhibitors displace BRD4 from MYC enhancers, BRD4 D1 inhibition in MM.1S cells is insufficient for stopping Myc expression and may lead to its upregulation. Future analysis of BRD4 D1 gene regulation may shed light on differential BET bromodomain functions.

中文翻译：

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通过靶向非保守残基和结构化水置换来选择性 N 末端 BET 溴结构域抑制剂**


溴结构域和末端外 (BET) 家族蛋白 BRD2-4 和 T 是重要的药物靶点；然而，每个溴结构域的生物学功能仍然不明确。尽管第一个 (D1) 和第二个 (D2) 布罗莫结构域的泛抑制剂是已知的，但仍缺乏选择性抑制单个 BET 布罗莫结构域的化学探针。在这里，我们开发了选择性 BET D1 抑制剂，优先结合 BRD4 D1。在竞争性抑制测定中，我们表明我们的先导化合物对 BRD4 D1 的选择性是其他 BET 溴结构域的 9-33 倍。 X 射线晶体学支持基于非保守赖氨酸的重组和 BRD4 D1 结合位点中相对于我们之前的先导物的额外结构水的置换的选择性的作用。尽管泛 D1 抑制剂取代了 MYC 增强子中的 BRD4，但 MM.1S 细胞中的 BRD4 D1 抑制不足以阻止 Myc 表达，并可能导致其上调。未来对 BRD4 D1 基因调控的分析可能会揭示 BET 溴结构域功能的差异。