Structural and Functional Analysis of the DEAF-1 and BS69 MYND Domains

DEAF-1 is an important transcriptional regulator that is required for embryonic development and is linked to clinical depression and suicidal behavior in humans. It comprises various structural domains, including a SAND domain that mediates DNA binding and a MYND domain, a cysteine-rich module organized in a Cys4-Cys2-His-Cys (C4-C2HC) tandem zinc binding motif. DEAF-1 transcription regulation activity is mediated through interactions with cofactors such as NCoR and SMRT. Despite the important biological role of the DEAF-1 protein, little is known regarding the structure and binding properties of its MYND domain.
Here, we report the solution structure, dynamics and ligand binding of the human DEAF-1 MYND domain encompassing residues 501–544 determined by NMR spectroscopy. The structure adopts a ββα fold that exhibits tandem zinc-binding sites with a cross-brace topology, similar to the MYND domains in AML1/ETO and other proteins. We show that the DEAF-1 MYND domain binds to peptides derived from SMRT and NCoR corepressors. The binding surface mapped by NMR titrations is similar to the one previously reported for AML1/ETO. The ligand binding and molecular functions of the related BS69 MYND domain were studied based on a homology model and mutational analysis. Interestingly, the interaction between BS69 and its binding partners (viral and cellular proteins) seems to require distinct charged residues flanking the predicted MYND domain fold, suggesting a different binding mode. Our findings demonstrate that the MYND domain is a conserved zinc binding fold that plays important roles in transcriptional regulation by mediating distinct molecular interactions with viral and cellular proteins.

DEAF-1是一类重要的转录调控因子，其不仅参与胚胎发育过程，还与人类的临床抑郁症及自杀行为密切相关。该蛋白包含多种结构域，其中包括介导DNA结合的SAND结构域（SAND domain），以及以Cys4-Cys2-His-Cys（C4-C2HC）串联锌结合基序排布的富半胱氨酸模块——MYND结构域（MYND domain）。DEAF-1的转录调控活性通过与NCoR、SMRT等辅因子的相互作用得以实现。尽管DEAF-1蛋白具有关键的生物学功能，但目前学界对其MYND结构域的结构特征与结合特性仍知之甚少。
本研究借助核磁共振光谱学（NMR spectroscopy），解析了人源DEAF-1中包含501至544位残基的MYND结构域的溶液结构、动力学性质及其配体结合特性。该结构采用ββα折叠模式，拥有十字支架拓扑结构的串联锌结合位点，与AML1/ETO及其他蛋白中的MYND结构域特征相似。实验结果表明，DEAF-1 MYND结构域可结合源自SMRT与NCoR辅阻遏因子的肽段。通过核磁共振滴定实验绘制的结合表面，与此前AML1/ETO的相关研究报道一致。
研究团队基于同源建模（homology model）与突变分析（mutational analysis），对相关BS69 MYND结构域的配体结合特性与分子功能展开了探究。值得注意的是，BS69与其结合伴侣（病毒蛋白与细胞蛋白）之间的相互作用，似乎需要位于预测MYND结构域折叠侧翼的特定带电残基参与，这提示二者的结合模式存在显著差异。本研究的实验结果证实，MYND结构域是一类保守的锌结合折叠单元，通过介导与病毒及细胞蛋白的特异性分子相互作用，在转录调控过程中发挥重要功能。