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Title: Identification of PP2A as a novel interactor and regulator of TRIP-Br1
Authors: Zang, Z.J.
Gunaratnam, L.
Cheong, J.K.
Hsiao, L.-L.
O'Leary, E.
Sun, X.
Bonventre, J.V.
Hsu, S.I.-H. 
Salto-Tellez, M. 
Lai, L.Y.
Keywords: E2F
Protein phosphatase
Issue Date: 2009
Citation: Zang, Z.J., Gunaratnam, L., Cheong, J.K., Hsiao, L.-L., O'Leary, E., Sun, X., Bonventre, J.V., Hsu, S.I.-H., Salto-Tellez, M., Lai, L.Y. (2009). Identification of PP2A as a novel interactor and regulator of TRIP-Br1. Cellular Signalling 21 (1) : 34-42. ScholarBank@NUS Repository.
Abstract: TRIP-Br proteins are a novel family of transcriptional coregulators involved in E2F-mediated cell cycle progression. Three of the four mammalian members of TRIP-Br family, including TRIP-Br1, are known oncogenes. We now report the identification of the Bα regulatory subunit of serine/threonine protein phosphatase 2A (PP2A) as a novel TRIP-Br1 interactor, based on an affinity binding assay coupled with mass spectrometry. A GST-TRIP-Br1 fusion protein associates with catalytically active PP2A-ABαC holoenzyme in vitro. Coimmunoprecipitation confirms this association in vivo. Immunofluorescence staining with a monoclonal antibody against TRIP-Br1 reveals that endogenous TRIP-Br1 and PP2A-Bα colocalize mainly in the cytoplasm. Consistently, immunoprecipitation followed by immunodetection with anti-phosphoserine antibody suggest that TRIP-Br1 exists in a serine-phosphorylated form. Inhibition of PP2A activity by okadaic acid or transcriptional silencing of the PP2A catalytic subunit by small interfering RNA results in downregulation of total TRIP-Br1 protein levels but upregulation of serine-phosphorylated TRIP-Br1. Overexpression of PP2A catalytic subunit increases TRIP-Br1 protein levels and TRIP-Br1 co-activated E2F1/DP1 transcription. Our data support a model in which association between PP2A-ABαC holoenzyme and TRIP-Br1 in vivo in mammalian cells represents a novel mechanism for regulating the level of TRIP-Br1 protooncoprotein. © 2008 Elsevier Inc. All rights reserved.
Source Title: Cellular Signalling
ISSN: 08986568
DOI: 10.1016/j.cellsig.2008.09.018
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