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Updated: Jun 28, 2026

A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
10:17

A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors

Published on: April 29, 2022

Identification of PP2A as a novel interactor and regulator of TRIP-Br1

Zhi Jiang Zang1, Lakshman Gunaratnam, Jit Kong Cheong

  • 1Renal Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.

Cellular Signalling
|October 23, 2008
PubMed

Insights

The serine/threonine protein phosphatase 2A (PP2A) Balpha subunit interacts with TRIP-Br1, a proto-oncogene involved in cell cycle regulation. This interaction influences TRIP-Br1 protein levels and phosphorylation, suggesting a novel regulatory mechanism.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • TRIP-Br proteins are transcriptional coregulators crucial for E2F-mediated cell cycle progression.
  • TRIP-Br1, a member of this family, is recognized as a proto-oncogene implicated in cancer development.

Purpose of the Study:

  • To identify novel interacting partners of TRIP-Br1.
  • To elucidate the functional relationship between TRIP-Br1 and protein phosphatase 2A (PP2A).

Main Methods:

  • Affinity binding assay coupled with mass spectrometry to identify TRIP-Br1 interactors.
  • GST-TRIP-Br1 fusion protein assays and co-immunoprecipitation to confirm in vitro and in vivo interactions.
  • Immunofluorescence microscopy for subcellular localization studies.
  • Functional assays involving PP2A inhibition (okadaic acid) and silencing (siRNA), and overexpression studies.

Main Results:

  • The Balpha regulatory subunit of PP2A was identified as a novel interactor of TRIP-Br1.
  • TRIP-Br1 and PP2A-Balpha colocalize in the cytoplasm, and TRIP-Br1 is serine-phosphorylated.
  • PP2A inhibition decreases total TRIP-Br1 but increases its serine-phosphorylated form; PP2A overexpression enhances TRIP-Br1 levels and co-activates E2F1/DP1 transcription.

Conclusions:

  • The association between PP2A-ABalphaC holoenzyme and TRIP-Br1 represents a novel mechanism for regulating TRIP-Br1 proto-oncogene levels in mammalian cells.
  • PP2A plays a critical role in modulating TRIP-Br1 protein stability and phosphorylation status, impacting its oncogenic function.

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