Intracellular signals triggered by DNA breakage flow through proteins containing BRCT (BRCA1 C-terminal) domains. This family, comprising 23 conserved phosphopeptide-binding modules in man, is inaccessible to small-molecule chemical inhibitors. Here, we develop Bractoppin, a drug-like inhibitor of phosphopeptide recognition by the human BRCA1 tandem (t)BRCT domain, which selectively inhibits substrate binding with nanomolar potencyin vitro. Structure-activity exploration suggests that Bractoppin engages BRCA1 tBRCT residues recognizing pSer in the consensus motif, pSer-Pro-Thr-Phe, plus an abutting hydrophobic pocket that is distinct in structurally related BRCT domains, conferring selectivity. In cells, Bractoppin inhibits substrate recognition detected by Förster resonance energy transfer, and diminishes BRCA1 recruitment to DNA breaks, in turn suppressing damage-induced G2 arrest and assembly of the recombinase, RAD51. But damage-induced MDC1 recruitment, single-stranded DNA (ssDNA) generation, and TOPBP1 recruitment remain unaffected. Thus, an inhibitor of phosphopeptide recognition selectively interrupts BRCA1 tBRCT-dependent signals evoked by DNA damage.

中文翻译：

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人 BRCA1 串联 BRCT 域靶向磷酸肽识别以中断 BRCA1 依赖性信号传导

由 DNA 断裂触发的细胞内信号流经含有 BRCT（BRCA1 C 末端）结构域的蛋白质。这个家族包含 23 个在人体中保守的磷酸肽结合模块，小分子化学抑制剂无法使用。在这里，我们开发了 Bractoppin，这是一种人类 BRCA1 串联 (t)BRCT 结构域对磷酸肽识别的类药物抑制剂，它在体外选择性地抑制底物与纳摩尔效价的结合。结构-活性探索表明，Bractoppin 与 BRCA1 tBRCT 残基结合，识别共有基序中的 pSer，pSer-Pro-Thr-Phe，加上在结构相关的 BRCT 结构域中不同的邻接疏水袋，赋予选择性。在细胞中，Bractoppin 抑制 Förster 共振能量转移检测到的底物识别，并减少 BRCA1 对 DNA 断裂的募集，反过来抑制损伤诱导的 G2 停滞和重组酶 RAD51 的组装。但损伤诱导的 MDC1 募集、单链 DNA (ssDNA) 生成和 TOPBP1 募集仍然不受影响。因此，磷酸肽识别抑制剂选择性地中断由 DNA 损伤引起的 BRCA1 tBRCT 依赖性信号。