title: Functional interactions between erythroid Krüppel-like factor (EKLF/KLF1) and protein phosphatase PPM1B/PP2Cβ.
abstract: 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.
authors.affiliation: Department of Developmental and Regenerative Biology, The Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Yvette Y
authors.initials: YY
authors.lastname: Yien
authors.forename: James J
authors.initials: JJ
authors.lastname: Bieker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D015704:CD4 Antigens / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D015672:Erythroid Precursor Cells / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D020014:K562 Cells; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D000071636:Protein Phosphatase 2C; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D055544:beta-Globins / Q000235:genetics
chemical_list: D015704:CD4 Antigens; C501168:KLF3 protein, human; D051741:Kruppel-Like Transcription Factors; D055544:beta-Globins; C080774:erythroid Kruppel-like factor; C000607457:PPM1B protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C