Department of Developmental and Regenerative Biology, The Mount Sinai School of Medicine, New York, New York 10029, USA.
J Biol Chem. 2012 May 4;287(19):15193-204. doi: 10.1074/jbc.M112.350496. Epub 2012 Mar 5.
Erythroid Krüppel-like factor (EKLF; KLF1) is an erythroid-specific transcription factor required for the transcription of genes that regulate erythropoiesis. In this paper, we describe the identification of a novel EKLF interactor, Ppm1b, a serine-threonine protein phosphatase that has been implicated in the attenuation of NFκB signaling and the regulation of Cdk9 phosphorylation status. We show that Ppm1b interacts with EKLF via its PEST1 sequence. However, its genetic regulatory role is complex. Using a promoter-reporter assay in an erythroid cell line, we show that Ppm1b superactivates EKLF at the β-globin and BKLF promoters, dependent on intact Ppm1b phosphatase activity. Conversely, depletion of Ppm1b in CD34(+) cells leads to a higher level of endogenous β-globin gene activation after differentiation. We also observe that Ppm1b likely has an indirect role in regulating EKLF turnover via its zinc finger domain. Together, these studies show that Ppm1b plays a multilayered role in regulating the availability and optimal activity of the EKLF protein in erythroid cells.
红细胞 Krüppel 样因子（EKLF；KLF1）是一种红细胞特异性转录因子，对于调节红细胞生成的基因的转录是必需的。在本文中，我们描述了一种新的 EKLF 相互作用蛋白 Ppm1b 的鉴定，它是一种丝氨酸-苏氨酸蛋白磷酸酶，已被牵涉到 NFκB 信号的衰减和 Cdk9 磷酸化状态的调节中。我们表明 Ppm1b 通过其 PEST1 序列与 EKLF 相互作用。然而，其遗传调控作用是复杂的。我们使用红细胞系中的启动子报告测定法表明，在 β-珠蛋白和 BKLF 启动子上，Ppm1b 依赖于完整的 Ppm1b 磷酸酶活性超激活 EKLF。相反，在 CD34(+)细胞中耗尽 Ppm1b 会导致分化后内源性 β-珠蛋白基因的激活水平更高。我们还观察到 Ppm1b 可能通过其锌指结构域在调节 EKLF 周转率方面发挥间接作用。总之，这些研究表明，Ppm1b 在调节红细胞中 EKLF 蛋白的可用性和最佳活性方面发挥了多层次的作用。
