Lei Ming, Feng Yue, Zhou Mengqi, Yang Yuan, Loppnau Peter, Li Yanjun, Yang Yi, Liu Yanli
Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan 430079, PR China; Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, Ontario M5G 1L7, Canada.
Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, Ontario M5G 1L7, Canada.
Biochem Biophys Res Commun. 2018 Feb 19;496(4):1344-1348. doi: 10.1016/j.bbrc.2018.02.016. Epub 2018 Feb 3.
RBBP1 is a retinoblastoma protein (pRb) binding protein acting as a repressor of gene transcription. RBBP1 is a multidomain protein including a chromo barrel domain, and its chromo barrel domain has been reported to recognize histone H4K20me3 weakly, and this binding is enhanced by the simultaneous binding of DNA. However, the molecular basis of this DNA-mediated histone binding by the chromo barrel domain of RBBP1 is unclear. Here we attempted to co-crystallize the chromo barrel domain of RBBP1 with either a histone H4K20me3 peptide alone or with both a histone H4K20me3 peptide and DNA, but only solved the peptide/DNA unbound crystal structure. Our structural analysis indicates that RBBP1 could interact with histone H4K20me3 similar to other histone binding chromo barrel domains, and the surface charge representation analysis of the chromo barrel domain of RBBP1 suggests that the chromo barrel domain of RBBP1 does not have a typical DNA binding surface, indicating that it might not bind to DNA. Consistently, our ITC assays also showed that DNA does not significantly enhance the histone binding ability of the chromo barrel domain of RBBP1.
RBBP1是一种视网膜母细胞瘤蛋白（pRb）结合蛋白，作为基因转录的抑制因子发挥作用。RBBP1是一种多结构域蛋白，包含一个染色质桶结构域，据报道其染色质桶结构域与组蛋白H4K20me3的结合较弱，并且这种结合会因DNA的同时结合而增强。然而，RBBP1的染色质桶结构域介导的这种DNA依赖性组蛋白结合的分子基础尚不清楚。在这里，我们尝试将RBBP1的染色质桶结构域与单独的组蛋白H4K20me3肽或与组蛋白H4K20me3肽和DNA一起进行共结晶，但仅解析出了肽/DNA未结合的晶体结构。我们的结构分析表明，RBBP1可以与组蛋白H4K20me3相互作用，类似于其他与组蛋白结合的染色质桶结构域，并且对RBBP1染色质桶结构域的表面电荷表征分析表明，RBBP1的染色质桶结构域没有典型的DNA结合表面，这表明它可能不与DNA结合。一致地，我们的等温滴定量热法（ITC）分析也表明，DNA不会显著增强RBBP1染色质桶结构域的组蛋白结合能力。
