UHRF1 is an important epigenetic regulator associated with apoptosis and tumour development. It is a multidomain protein that integrates readout of different histone modification states and DNA methylation with enzymatic histone ubiquitylation activity. Emerging evidence indicates that the chromatin-binding and enzymatic modules of UHRF1 do not act in isolation but interplay in a coordinated and regulated manner. Here, we compared two splicing variants (V1, V2) of murine UHRF1 (mUHRF1) with human UHRF1 (hUHRF1). We show that insertion of nine amino acids in a linker region connecting the different TTD and PHD histone modification-binding domains causes distinct H3K9me3-binding behaviour of mUHRF1 V1. Structural analysis suggests that in mUHRF1 V1, in contrast to V2 and hUHRF1, the linker is anchored in a surface groove of the TTD domain, resulting in creation of a coupled TTD-PHD module. This establishes multivalent, synergistic H3-tail binding causing distinct cellular localization and enhanced H3K9me3-nucleosome ubiquitylation activity. In contrast to hUHRF1, H3K9me3-binding of the murine proteins is not allosterically regulated by phosphatidylinositol 5-phosphate that interacts with a separate less-conserved polybasic linker region of the protein. Our results highlight the importance of flexible linkers in regulating multidomain chromatin binding proteins and point to divergent evolution of their regulation.

中文翻译：

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选择性剪接和变构调节可调节UHRF1的染色质结合。

UHRF1是与细胞凋亡和肿瘤发展相关的重要表观遗传调控因子。它是一种多域蛋白，整合了不同组蛋白修饰状态的读数和具有酶促组蛋白泛素化活性的DNA甲基化。越来越多的证据表明，UHRF1的染色质结合和酶促模块不是孤立地起作用，而是以协调和调控的方式相互作用。在这里，我们比较了小鼠UHRF1（mUHRF1）与人UHRF1（hUHRF1）的两个剪接变体（V1，V2）。我们显示在连接不同的TTD和PHD组蛋白修饰结合域的接头区域中插入9个氨基酸会引起mUHRF1 V1的独特H3K9me3结合行为。结构分析表明，与V2和hUHRF1相比，在mUHRF1 V1中，连接子锚定在TTD域的表面凹槽中，从而创建了一个耦合的TTD-PHD模块。这建立了多价的，协同的H3尾部绑定，导致不同的细胞定位和增强的H3K9me3核小体泛素化活性。与hUHRF1相反，鼠蛋白的H3K9me3结合不受磷脂酰肌醇5-磷酸与蛋白质的一个单独的保守程度较低的多元连接子区域相互作用的变构调节。我们的结果突出了柔性接头在调节多域染色质结合蛋白中的重要性，并指出了其调节的不同演变。鼠蛋白的H3K9me3结合不受磷脂酰肌醇5-磷酸与蛋白质的一个单独的保守程度较低的多元连接子区域相互作用的变构调控。我们的结果突出了柔性接头在调节多域染色质结合蛋白中的重要性，并指出了其调节的不同演变。鼠蛋白的H3K9me3结合不受磷脂酰肌醇5-磷酸与蛋白质的一个单独的保守程度较低的多元连接子区域相互作用的变构调节。我们的结果突出了柔性接头在调节多域染色质结合蛋白中的重要性，并指出了其调节的不同演变。