National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100089, China.
National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
J Genet Genomics. 2021 Jun 20;48(6):463-472. doi: 10.1016/j.jgg.2021.04.007. Epub 2021 May 26.
Centromeres are chromosomal loci marked by histone variant CenH3 (centromeric histone H3) and essential for genomic stability and cell division. The budding yeast E3 ubiquitin ligase Psh1 selectively recognizes the yeast CenH3 (Cse4) for ubiquitination and controls the cellular level of Cse4 for proteolysis, but the underlying mechanism remains largely unknown. Here, we show that Psh1 uses a Cse4-binding domain (CBD, residues 1-211) to interact with Cse4-H4 instead of H3-H4, yielding a dissociation constant (K) of 27 nM. Psh1 recognizes Cse4-specific residues in the L1 loop and α2 helix to ensure Cse4 binding and ubiquitination. We map the Psh1-binding region of Cse4-H4 and identify a wide range of Cse4-specific residues required for the Psh1-mediated Cse4 recognition and ubiquitination. Further analyses reveal that histone chaperone Scm3 can impair Cse4 ubiquitination by abrogating Psh1-Cse4 binding. Together, our study reveals a novel Cse4-binding mode distinct from those of known CenH3 chaperones and elucidates the mechanism by which Scm3 competes with Psh1 for Cse4 binding.
着丝粒是由组蛋白变体 CenH3（着丝粒组蛋白 H3）标记的染色体位置，对于基因组稳定性和细胞分裂至关重要。芽殖酵母 E3 泛素连接酶 Psh1 选择性识别酵母 CenH3（Cse4）进行泛素化，并控制 Cse4 的细胞水平进行蛋白水解，但潜在的机制在很大程度上仍然未知。在这里，我们表明 Psh1 使用 Cse4 结合结构域（CBD，残基 1-211）与 Cse4-H4 而不是 H3-H4 相互作用，产生解离常数（K）为 27 nM。Psh1 识别 L1 环和 α2 螺旋中的 Cse4 特异性残基，以确保 Cse4 结合和泛素化。我们绘制了 Cse4-H4 的 Psh1 结合区域，并确定了广泛的 Cse4 特异性残基，这些残基对于 Psh1 介导的 Cse4 识别和泛素化是必需的。进一步的分析表明，组蛋白伴侣 Scm3 可以通过废除 Psh1-Cse4 结合来破坏 Cse4 泛素化。总之，我们的研究揭示了一种与已知 CenH3 伴侣不同的新型 Cse4 结合模式，并阐明了 Scm3 如何与 Psh1 竞争 Cse4 结合的机制。
