Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, 29425, USA.
Sci Rep. 2022 Jul 1;12(1):11210. doi: 10.1038/s41598-022-15339-8.
Protein kinases that phosphorylate histones are ideally-placed to influence the behavior of chromosomes during cell division. Indeed, a number of conserved histone phosphorylation events occur prominently during mitosis and meiosis in most eukaryotes, including on histone H3 at threonine-3 (H3T3ph). At least two kinases, Haspin and VRK1 (NHK-1/ballchen in Drosophila), have been proposed to carry out this modification. Phosphorylation of H3 by Haspin has defined roles in mitosis, but the significance of VRK1 activity towards histones in dividing cells has been unclear. Here, using in vitro kinase assays, KiPIK screening, RNA interference, and CRISPR/Cas9 approaches, we were unable to substantiate a direct role for VRK1, or its paralogue VRK2, in the phosphorylation of threonine-3 or serine-10 of Histone H3 in mitosis, although loss of VRK1 did slow cell proliferation. We conclude that the role of VRKs, and their more recently identified association with neuromuscular disease and importance in cancers of the nervous system, are unlikely to involve mitotic histone kinase activity. In contrast, Haspin is required to generate H3T3ph during mitosis.
磷酸化组蛋白的蛋白激酶在影响细胞分裂过程中染色体的行为方面具有得天独厚的优势。事实上，在大多数真核生物中，包括在组蛋白 H3 的苏氨酸-3（H3T3ph）上，有许多保守的组蛋白磷酸化事件在有丝分裂和减数分裂中明显发生。至少有两种激酶，Haspin 和 VRK1（果蝇中的 NHK-1/ballchen），被提议进行这种修饰。Haspin 对 H3 的磷酸化在有丝分裂中具有明确的作用，但 VRK1 对分裂细胞中组蛋白的活性的意义尚不清楚。在这里，我们使用体外激酶测定、KiPIK 筛选、RNA 干扰和 CRISPR/Cas9 方法，未能证实 VRK1 或其同源物 VRK2 在有丝分裂中直接磷酸化组蛋白 H3 的苏氨酸-3 或丝氨酸-10，尽管 VRK1 的缺失确实会减缓细胞增殖。我们得出结论，VRK 的作用，以及它们最近与神经肌肉疾病的关联及其在神经系统癌症中的重要性，不太可能涉及有丝分裂组蛋白激酶活性。相比之下，Haspin 在有丝分裂过程中生成 H3T3ph 是必需的。
