Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA.
Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA; Broad Institute of Harvard and MIT, 415 Main Street, Cambridge, MA 02142, USA.
Mol Cell. 2019 Mar 7;73(5):985-1000.e6. doi: 10.1016/j.molcel.2019.01.004. Epub 2019 Jan 30.
Hyper-phosphorylation of RB controls its interaction with E2F and inhibits its tumor suppressor properties. However, during G1 active RB can be mono-phosphorylated on any one of 14 CDK phosphorylation sites. Here, we used quantitative proteomics to profile protein complexes formed by each mono-phosphorylated RB isoform (mP-RB) and identified the associated transcriptional outputs. The results show that the 14 sites of mono-phosphorylation co-ordinate RB's interactions and confer functional specificity. All 14 mP-RBs interact with E2F/DP proteins, but they provide different shades of E2F regulation. RB mono-phosphorylation at S811, for example, alters RB transcriptional activity by promoting its association with NuRD complexes. The greatest functional differences between mP-RBs are evident beyond the cell cycle machinery. RB mono-phosphorylation at S811 or T826 stimulates the expression of oxidative phosphorylation genes, increasing cellular oxygen consumption. These results indicate that RB activation signals are integrated in a phosphorylation code that determines the diversity of RB activity.
RB 的过度磷酸化控制其与 E2F 的相互作用，并抑制其肿瘤抑制特性。然而，在 G1 期，RB 可在 14 个 CDK 磷酸化位点中的任何一个上被单磷酸化。在这里，我们使用定量蛋白质组学来描绘每个单磷酸化 RB 异构体（mP-RB）形成的蛋白质复合物，并鉴定相关的转录产物。结果表明，14 个单磷酸化位点协调 RB 的相互作用并赋予功能特异性。所有 14 个 mP-RB 都与 E2F/DP 蛋白相互作用，但它们提供不同程度的 E2F 调节。例如，RB 在 S811 的单磷酸化通过促进其与 NuRD 复合物的结合来改变 RB 的转录活性。mP-RB 之间最大的功能差异在细胞周期机制之外表现得最为明显。RB 在 S811 或 T826 的单磷酸化刺激氧化磷酸化基因的表达，增加细胞的耗氧量。这些结果表明，RB 的激活信号被整合到一个磷酸化密码中，该密码决定了 RB 活性的多样性。
