School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia.
School of Chemistry, University of Sydney, New South Wales, Australia.
J Biol Chem. 2023 Dec;299(12):105482. doi: 10.1016/j.jbc.2023.105482. Epub 2023 Nov 20.
Bromodomains (BDs) regulate gene expression by recognizing protein motifs containing acetyllysine. Although originally characterized as histone-binding proteins, it has since become clear that these domains interact with other acetylated proteins, perhaps most prominently transcription factors. The likely transient nature and low stoichiometry of such modifications, however, has made it challenging to fully define the interactome of any given BD. To begin to address this knowledge gap in an unbiased manner, we carried out mRNA display screens against a BD-the N-terminal BD of BRD3-using peptide libraries that contained either one or two acetyllysine residues. We discovered peptides with very strong consensus sequences and with affinities that are significantly higher than typical BD-peptide interactions. X-ray crystal structures also revealed modes of binding that have not been seen with natural ligands. Intriguingly, however, our sequences are not found in the human proteome, perhaps suggesting that strong binders to BDs might have been selected against during evolution.
溴结构域 (BD) 通过识别含有乙酰赖氨酸的蛋白质基序来调节基因表达。虽然最初被描述为组蛋白结合蛋白，但后来清楚的是，这些结构域与其他乙酰化蛋白相互作用，也许最突出的是转录因子。然而，这种修饰的可能短暂性质和低化学计量，使得完全定义任何给定 BD 的相互作用组成为一项挑战。为了以无偏倚的方式开始解决这一知识空白，我们使用含有一个或两个乙酰赖氨酸残基的肽文库，针对 BD（BRD3 的 N 端 BD）进行了 mRNA 显示筛选。我们发现了具有非常强的共识序列的肽，并且亲和力明显高于典型的 BD-肽相互作用。X 射线晶体结构还揭示了与天然配体不同的结合模式。有趣的是，然而，我们的序列在人类蛋白质组中没有发现，这也许表明，BD 的强结合物可能在进化过程中被选择所淘汰。
