García-González Raúl, Morejón-García Patricia, Campillo-Marcos Ignacio, Salzano Marcella, Lazo Pedro A
Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain.
Área de Cancer, Instituto de Investigación Biomédica de Salamanca-IBSAL, Hospital Universitario de Salamanca, 37007 Salamanca, Spain.
Cancers (Basel). 2020 Oct 15;12(10):2986. doi: 10.3390/cancers12102986.
Dynamic remodeling of chromatin requires acetylation and methylation of histones, frequently affecting the same lysine residue. These alternative epigenetic modifications require the coordination of enzymes, writers and erasers, mediating them such as acetylases and deacetylases. In cells in G0/G1, DNA damage induced by doxorubicin causes an increase in histone H4K16ac, a marker of chromatin relaxation. In this context, we studied the role that VRK1, a chromatin kinase activated by DNA damage, plays in this early step. VRK1 depletion or MG149, a Tip60/KAT5 inhibitor, cause a loss of H4K16ac. DNA damage induces the phosphorylation of Tip60 mediated by VRK1 in the chromatin fraction. VRK1 directly interacts with and phosphorylates Tip60. Furthermore, the phosphorylation of Tip60 induced by doxorubicin is lost by depletion of VRK1 in both +/+ and -/- cells. Kinase-active VRK1, but not kinase-dead VRK1, rescues Tip60 phosphorylation induced by DNA damage independently of ATM. The Tip60 phosphorylation by VRK1 is necessary for the activating acetylation of ATM, and subsequent ATM autophosphorylation, and both are lost by VRK1 depletion. These results support that the VRK1 chromatin kinase is an upstream regulator of the initial acetylation of histones, and an early step in DNA damage responses (DDR).
染色质的动态重塑需要组蛋白的乙酰化和甲基化，这常常影响相同的赖氨酸残基。这些替代性的表观遗传修饰需要酶、“书写者”和“擦除者”之间的协调，由诸如乙酰转移酶和去乙酰化酶来介导。在G0/G1期的细胞中，阿霉素诱导的DNA损伤会导致组蛋白H4K16ac增加，这是染色质松弛的一个标志物。在此背景下，我们研究了由DNA损伤激活的染色质激酶VRK1在这一早期步骤中所起的作用。VRK1缺失或Tip60/KAT5抑制剂MG149会导致H4K16ac缺失。DNA损伤会诱导染色质部分中由VRK1介导的Tip60磷酸化。VRK1直接与Tip60相互作用并使其磷酸化。此外，在+/+和-/-细胞中，阿霉素诱导的Tip60磷酸化会因VRK1缺失而消失。激酶活性的VRK1而非激酶失活的VRK1可独立于ATM挽救由DNA损伤诱导的Tip60磷酸化。VRK1介导的Tip60磷酸化对于ATM的激活乙酰化以及随后的ATM自身磷酸化是必需的，而这两者都会因VRK1缺失而消失。这些结果支持VRK1染色质激酶是组蛋白初始乙酰化的上游调节因子，也是DNA损伤反应（DDR）的早期步骤。
