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PP2A-B55 and its adapter proteins IER2 and IER5 regulate the activity of RB family proteins and the expression of cell cycle-related genes
The FEBS Journal ( IF 5.5 ) Pub Date : 2022-09-01 , DOI: 10.1111/febs.16612
Kuriko Doi 1 , Hiroto Takeuchi 1 , Hiroshi Sakurai 1
Affiliation  

The retinoblastoma (RB) tumour suppressor protein regulates cell proliferation, motility, differentiation and apoptosis. The phosphorylation state of RB is modulated by kinases and phosphatases, and RB exhibits phosphorylation-sensitive interactions with E2F family transcription factors. Here, we characterize RB dephosphorylation by protein phosphatase 2A (PP2A). The growth factor-inducible immediate early response (IER) proteins IER2 and IER5 possess an adapter-like function in which IER proteins bind to both PP2A and its target proteins and enhance PP2A activity towards the proteins. IER2 interacts with RB and facilitates dephosphorylation of RB at T821/T826 by PP2A. In IER2 knockdown cells, elevated phosphorylation of RB resulted in reduced binding of RB to the promoters and derepression of cyclin D1 and p21. IER5 binds to both RB and RB-like 1 (p107/RBL1), enhances dephosphorylation of these proteins by PP2A and represses the expression of various cell cycle-related genes. However, IER2-regulated dephosphorylation at T821/T826 is not necessary for the repression function of RB in cell mobility-related gene expression. Our data identify PP2A adapter proteins as critical regulators of RB family proteins and suggest that the phosphorylation status of RB differentially affects gene expression.

中文翻译:

PP2A-B55及其衔接蛋白IER2和IER5调节RB家族蛋白的活性和细胞周期相关基因的表达

视网膜母细胞瘤 (RB) 肿瘤抑制蛋白调节细胞增殖、运动、分化和凋亡。RB 的磷酸化状态受激酶和磷酸酶调节,并且 RB 与 E2F 家族转录因子表现出磷酸化敏感的相互作用。在这里,我们通过蛋白磷酸酶 2A (PP2A) 表征 RB 去磷酸化。生长因子诱导的立即早期反应 (IER) 蛋白 IER2 和 IER5 具有类似接头的功能,其中 IER 蛋白与 PP2A 及其靶蛋白结合并增强 PP2A 对蛋白质的活性。IER2 与 RB 相互作用并通过 PP2A 促进 RB 在 T821/T826 位点的去磷酸化。在 IER2 敲低细胞中,RB 的磷酸化升高导致 RB 与启动子的结合减少以及细胞周期蛋白 D1 和 p21 的去阻遏。IER5 与 RB 和 RB 样 1 (p107/RBL1) 结合,通过 PP2A 增强这些蛋白质的去磷酸化并抑制各种细胞周期相关基因的表达。然而,IER2 调节的 T821/T826 去磷酸化对于 RB 在细胞迁移相关基因表达中的抑制功能不是必需的。我们的数据将 PP2A 衔接蛋白鉴定为 RB 家族蛋白的关键调节因子,并表明 RB 的磷酸化状态对基因表达有不同的影响。
更新日期:2022-09-01
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