Structural Biochemistry & Molecular Biophysics Laboratory, Department of Biochemistry, College of Life Sciences & Biotechnology, Yonsei University, Seoul, 120-749, South Korea.
Structural Biochemistry & Molecular Biophysics Laboratory, Department of Biochemistry, College of Life Sciences & Biotechnology, Yonsei University, Seoul, 120-749, South Korea.
Biochem Biophys Res Commun. 2020 Dec 17;533(4):919-924. doi: 10.1016/j.bbrc.2020.09.094. Epub 2020 Sep 30.
The SWI/SNF chromatin remodeling complex plays important roles in gene regulation and it is classified as the SWI/SNF complex in yeast and BAF complex in vertebrates. BAF57, one of the subunits that forms the chromatin remodeling complex core, is well conserved in the BAF complex of vertebrates, which is replaced by bap111 in the Drosophila BAP complex and does not have a counterpart in the yeast SWI/SNF complex. This suggests that BAF57 is a key component of the chromatin remodeling complex in higher eukaryotes. BAF57 contains a HMG domain, which is widely distributed among various proteins and functions as a DNA binding motif. Most proteins with HMG domain bind to four-way junction (4WJ) DNA. Here, we report the crystal structure of the HMG domain of BAF57 (BAF57) at a resolution of 2.55 Å. The structure consists of three α-helices and adopts an L-shaped form. The overall structure is stabilized by a hydrophobic core, which is formed by hydrophobic residues. The binding affinity between BAF57 and 4WJ DNA is determined as a 295.83 ± 1.05 nM using a fluorescence quenching assay, and the structure revealed 4WJ DNA binding site of BAF57. Our data will serve structural basis in understanding the roles of BAF57 during chromatin remodeling process.
SWI/SNF 染色质重塑复合物在基因调控中发挥着重要作用，它在酵母中被归类为 SWI/SNF 复合物，在脊椎动物中被归类为 BAF 复合物。BAF57 是形成染色质重塑复合物核心的亚基之一，在脊椎动物的 BAF 复合物中高度保守，而在果蝇 BAP 复合物中被 bap111 取代，在酵母 SWI/SNF 复合物中没有对应物。这表明 BAF57 是高等真核生物染色质重塑复合物的关键组成部分。BAF57 含有一个 HMG 结构域，该结构域广泛分布于各种蛋白质中，作为 DNA 结合基序发挥作用。大多数具有 HMG 结构域的蛋白质与四向连接（4WJ）DNA 结合。在这里，我们报道了 BAF57（BAF57）HMG 结构域的晶体结构，分辨率为 2.55Å。该结构由三个α-螺旋组成，采用 L 形形式。整体结构由疏水性核心稳定，疏水性核心由疏水性残基形成。使用荧光猝灭实验确定 BAF57 与 4WJ DNA 的结合亲和力为 295.83±1.05nM，结构揭示了 BAF57 的 4WJ DNA 结合位点。我们的数据将为理解 BAF57 在染色质重塑过程中的作用提供结构基础。
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