Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, California 95064, USA.
Division of Hematology, Oncology and Palliative Care and Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
Nat Commun. 2016 Jul 28;7:12301. doi: 10.1038/ncomms12301.
The MuvB complex recruits transcription factors to activate or repress genes with cell cycle-dependent expression patterns. MuvB contains the DNA-binding protein LIN54, which directs the complex to promoter cell cycle genes homology region (CHR) elements. Here we characterize the DNA-binding properties of LIN54 and describe the structural basis for recognition of a CHR sequence. We biochemically define the CHR consensus as TTYRAA and determine that two tandem cysteine rich regions are required for high-affinity DNA association. A crystal structure of the LIN54 DNA-binding domain in complex with a CHR sequence reveals that sequence specificity is conferred by two tyrosine residues, which insert into the minor groove of the DNA duplex. We demonstrate that this unique tyrosine-mediated DNA binding is necessary for MuvB recruitment to target promoters. Our results suggest a model in which MuvB binds near transcription start sites and plays a role in positioning downstream nucleosomes.
MuvB 复合物招募转录因子，以激活或抑制具有细胞周期依赖性表达模式的基因。MuvB 包含 DNA 结合蛋白 LIN54，它指导复合物靶向启动子细胞周期基因同源区 (CHR) 元件。在这里，我们描述了 LIN54 的 DNA 结合特性，并描述了识别 CHR 序列的结构基础。我们通过生化方法定义了 CHR 的共识序列为 TTYRAA，并确定两个串联的富含半胱氨酸的区域是高亲和力 DNA 结合所必需的。LIN54 DNA 结合域与 CHR 序列的复合物的晶体结构表明，序列特异性由两个插入 DNA 双螺旋小沟的酪氨酸残基赋予。我们证明，这种独特的酪氨酸介导的 DNA 结合对于 MuvB 复合物招募到靶启动子是必要的。我们的结果表明，MuvB 复合物结合在转录起始位点附近，并在定位下游核小体中发挥作用。
