VIB Center for Structural Biology, Vrije Universiteit Brussel, Pleinlaan, 2 1050, Brussels, Belgium.
Department of Physics and Astronomy, Clemson University, Clemson, SC, 29634, USA.
Nat Commun. 2019 Apr 11;10(1):1676. doi: 10.1038/s41467-019-09446-w.
p27 is an intrinsically disordered protein (IDP) that inhibits cyclin-dependent kinase (Cdk)/cyclin complexes (e.g., Cdk2/cyclin A), causing cell cycle arrest. Cell division progresses when stably Cdk2/cyclin A-bound p27 is phosphorylated on one or two structurally occluded tyrosine residues and a distal threonine residue (T187), triggering degradation of p27. Here, using an integrated biophysical approach, we show that Cdk2/cyclin A-bound p27 samples lowly-populated conformations that provide access to the non-receptor tyrosine kinases, BCR-ABL and Src, which phosphorylate Y88 or Y88 and Y74, respectively, thereby promoting intra-assembly phosphorylation (of p27) on distal T187. Even when tightly bound to Cdk2/cyclin A, intrinsic flexibility enables p27 to integrate and process signaling inputs, and generate outputs including altered Cdk2 activity, p27 stability, and, ultimately, cell cycle progression. Intrinsic dynamics within multi-component assemblies may be a general mechanism of signaling by regulatory IDPs, which can be subverted in human disease.
p27 是一种固有无序蛋白（IDP），它能抑制周期蛋白依赖性激酶（Cdk）/周期蛋白复合物（如 Cdk2/周期蛋白 A），导致细胞周期停滞。当稳定结合的 Cdk2/周期蛋白 A 的 p27 上的一个或两个结构上被掩盖的酪氨酸残基和一个远端苏氨酸残基（T187）被磷酸化时，细胞分裂会继续进行，从而触发 p27 的降解。在这里，我们使用一种综合的生物物理方法表明，Cdk2/周期蛋白 A 结合的 p27 会采用低丰度构象，这些构象能与非受体酪氨酸激酶 BCR-ABL 和 Src 结合，这两种激酶分别磷酸化 Y88 或 Y88 和 Y74，从而促进远端 T187 上的组装内磷酸化（p27）。即使与 Cdk2/周期蛋白 A 紧密结合，固有灵活性也使 p27 能够整合和处理信号输入，并产生包括改变 Cdk2 活性、p27 稳定性以及最终细胞周期进程的输出。多组分组装内的固有动力学可能是调节 IDP 信号转导的一般机制，在人类疾病中可能会被颠覆。
