Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
Biochem Biophys Res Commun. 2010 Mar 12;393(3):504-8. doi: 10.1016/j.bbrc.2010.02.035. Epub 2010 Feb 10.
In spite of its central roles in cell cycle progression, senescence, and aging, knowledge about the posttranslational regulation of P16 (also known as INK4A and MTS1) remains limited. While it has been reported that P16 could be phosphorylated at Ser7, Ser8, Ser140, and Ser152, the corresponding kinases have not been identified yet. Here we report that IKKbeta, a primary kinase for IkappaBalpha phosphorylation, is involved in P16 phosphorylation. Immunoprecipitation and kinase assays showed that IKKbeta specifically binds to P16 and phosphorylates P16 at Ser8 in WI38 cells. Biochemical characterization of phosphomimetic Ser-->Glu P16 mutants demonstrated that phosphorylation at Ser8 of P16 brings about a significant loss of its cyclin-dependent kinase (CDK) 4-inhibitory activity while P16 retains structurally and functionally intact upon phosphorylation at Ser7, Ser140, and Ser152. Our results reveal the novel role of IKKbeta in P16 phosphorylation and broaden our understanding of the regulation of P16.
尽管 P16（也称为 INK4A 和 MTS1）在细胞周期进程、衰老和老化中发挥着核心作用，但对其翻译后调节的了解仍然有限。虽然已经报道 P16 可以在 Ser7、Ser8、Ser140 和 Ser152 处被磷酸化，但相应的激酶尚未被鉴定。在这里，我们报告说，IKKbeta，一种用于 IkappaBalpha 磷酸化的主要激酶，参与了 P16 的磷酸化。免疫沉淀和激酶测定表明，IKKbeta 特异性地与 P16 结合，并在 WI38 细胞中在 Ser8 处磷酸化 P16。磷酸模拟 Ser-->Glu P16 突变体的生化特性表明，P16 在 Ser8 处的磷酸化导致其对细胞周期蛋白依赖性激酶 (CDK) 4 的抑制活性显著丧失，而 P16 在 Ser7、Ser140 和 Ser152 处磷酸化时保持结构和功能完整。我们的结果揭示了 IKKbeta 在 P16 磷酸化中的新作用，并拓宽了我们对 P16 调节的理解。
