Muthurajan Uma M, Bao Yunhe, Forsberg Lawrence J, Edayathumangalam Rajeswari S, Dyer Pamela N, White Cindy L, Luger Karolin
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA.
EMBO J. 2004 Jan 28;23(2):260-71. doi: 10.1038/sj.emboj.7600046. Epub 2004 Jan 22.
Here we describe 11 crystal structures of nucleosome core particles containing individual point mutations in the structured regions of histones H3 and H4. The mutated residues are located at the two protein-DNA interfaces flanking the nucleosomal dyad. Five of the mutations partially restore the in vivo effects of SWI/SNF inactivation in yeast. We find that even nonconservative mutations of these residues (which exhibit a distinct phenotype in vivo) have only moderate effects on global nucleosome structure. Rather, local protein-DNA interactions are disrupted and weakened in a subtle and complex manner. The number of lost protein-DNA interactions correlates directly with an increased propensity of the histone octamer to reposition with respect to the DNA, and with an overall destabilization of the nucleosome. Thus, the disruption of only two to six of the approximately 120 direct histone-DNA interactions within the nucleosome has a pronounced effect on nucleosome mobility and stability. This has implications for our understanding of how these structures are made accessible to the transcription and replication machinery in vivo.
在此，我们描述了11种核小体核心颗粒的晶体结构，这些核小体核心颗粒在组蛋白H3和H4的结构化区域含有单个点突变。突变残基位于核小体二分体两侧的两个蛋白质-DNA界面处。其中五个突变部分恢复了酵母中SWI/SNF失活的体内效应。我们发现，即使这些残基的非保守突变（在体内表现出明显的表型）对整体核小体结构也只有适度影响。相反，局部蛋白质-DNA相互作用以微妙而复杂的方式被破坏和削弱。丢失的蛋白质-DNA相互作用的数量与组蛋白八聚体相对于DNA重新定位的倾向增加直接相关，也与核小体的整体不稳定相关。因此，核小体内大约120个直接组蛋白-DNA相互作用中仅两到六个的破坏，就对核小体的移动性和稳定性产生了显著影响。这对于我们理解这些结构在体内如何被转录和复制机制所接近具有重要意义。
