Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Sapienza University of Rome, 00185 Rome, Italy.
ENEA CR Frascati, Diagnostics and Metrology Laboratory FSN-TECFIS-DIM, 00044 Rome, Italy.
Int J Mol Sci. 2021 May 31;22(11):5953. doi: 10.3390/ijms22115953.
Bromodomains (BRDs) are small protein interaction modules of about 110 amino acids that selectively recognize acetylated lysine in histones and other proteins. These domains have been identified in a variety of multi-domain proteins involved in transcriptional regulation or chromatin remodeling in eukaryotic cells. BRD inhibition is considered an attractive therapeutic approach in epigenetic disorders, particularly in oncology. Here, we present a Φ value analysis to investigate the folding pathway of the second domain of BRD2 (BRD2(2)). Using an extensive mutational analysis based on 25 site-directed mutants, we provide structural information on both the intermediate and late transition state of BRD2(2). The data reveal that the C-terminal region represents part of the initial folding nucleus, while the N-terminal region of the domain consolidates its structure only later in the folding process. Furthermore, only a small number of native-like interactions have been identified, suggesting the presence of a non-compact, partially folded state with scarce native-like characteristics. Taken together, these results indicate that, in BRD2(2), a hierarchical mechanism of protein folding can be described with non-native interactions that play a significant role in folding.
溴结构域（BRDs）是约 110 个氨基酸的小蛋白相互作用模块，选择性地识别组蛋白和其他蛋白质中乙酰化的赖氨酸。这些结构域已在涉及真核细胞中转录调节或染色质重塑的各种多结构域蛋白中被鉴定出来。BRD 抑制被认为是表观遗传紊乱的一种有吸引力的治疗方法，特别是在肿瘤学中。在这里，我们进行了Φ 值分析，以研究 BRD2（BRD2(2)）的第二个结构域的折叠途径。通过基于 25 个定点突变体的广泛突变分析，我们提供了 BRD2(2)的中间和晚期过渡态的结构信息。数据表明，C 末端区域代表初始折叠核的一部分，而结构域的 N 末端区域仅在折叠过程的后期才巩固其结构。此外，只鉴定出少数具有天然类似特征的相互作用，表明存在非紧凑的、部分折叠的状态，具有很少的天然类似特征。总之，这些结果表明，在 BRD2(2)中，可以用非天然相互作用来描述蛋白质折叠的层次机制，这些相互作用在折叠中起着重要的作用。
