The B55α/PP2A Holoenzyme in Cell Cycle Exit, Maturation/Differentiation, and Cancer
type: CreativeWork
description: The cell cycle is negatively regulated by members of the pocket protein family, which consists of the tumor suppressor pRB and two closely related paralogs, p107 and p130. In their hypophosphorylated state, they are associated with E2F transcription factors which result in the repression of transcription of E2F-dependent genes that are required for cell cycle progression. The phosphorylation state of pocket proteins during the cell cycle is determined at least in part by an equilibrium between inducible CDKs and the serine/threonine protein phosphatase PP2A. Protein Phosphatase 2A (PP2A), is a serine/threonine phosphatase that functions as as a collection of trimeric holoenzymes. The trimeric PP2A holoenzyme is composed of the "A" scaffolding subunit, the "C" catalytic subunit, and a "B" regulatory subunit. The B subunit is the major determinant in substrate specificity and subcellular localization. Two holoenzymes consisting of the core PP2A dimer and either the B55α or PR70 regulatory subunits have been implicated in the activation of p107/p130 and pRB, respectively. While the phosphorylation state of p107 is very sensitive to forced changes of B55α levels in human cell lines, regulation of p107 in response to physiological modulation of PP2A/B55α has not been previously elucidated. In this thesis, I show that FGF1, which induces maturation and cell cycle exit in chondrocytes, triggers rapid accumulation of p107/PP2A/B55α complexes coinciding with p107 dephosphorylation without an increase in B55α protein expression in RCS cells. Reciprocal solution-based mass-spectrometry analysis identified the PP2A/B55α complex as a major component of a subset of p107 complexes, which also contain E2F/DPs, DREAM subunits and cyclin/CDK complexes. p107 is one of the major partners of B55α, which also associates with pRB in RCS cells. FGF1 induces dephosphorylation of p107, its translocation to the nucleus, remodeling of p107 complexes, and enhances its interaction with E2F4 and …
abstract: The cell cycle is negatively regulated by members of the pocket protein family, which consists of the tumor suppressor pRB and two closely related paralogs, p107 and p130. In their hypophosphorylated state, they are associated with E2F transcription factors which result in the repression of transcription of E2F-dependent genes that are required for cell cycle progression. The phosphorylation state of pocket proteins during the cell cycle is determined at least in part by an equilibrium between inducible CDKs and the serine/threonine protein phosphatase PP2A. Protein Phosphatase 2A (PP2A), is a serine/threonine phosphatase that functions as as a collection of trimeric holoenzymes. The trimeric PP2A holoenzyme is composed of the "A" scaffolding subunit, the "C" catalytic subunit, and a "B" regulatory subunit. The B subunit is the major determinant in substrate specificity and subcellular localization. Two holoenzymes consisting of the core PP2A dimer and either the B55α or PR70 regulatory subunits have been implicated in the activation of p107/p130 and pRB, respectively. While the phosphorylation state of p107 is very sensitive to forced changes of B55α levels in human cell lines, regulation of p107 in response to physiological modulation of PP2A/B55α has not been previously elucidated. In this thesis, I show that FGF1, which induces maturation and cell cycle exit in chondrocytes, triggers rapid accumulation of p107/PP2A/B55α complexes coinciding with p107 dephosphorylation without an increase in B55α protein expression in RCS cells. Reciprocal solution-based mass-spectrometry analysis identified the PP2A/B55α complex as a major component of a subset of p107 complexes, which also contain E2F/DPs, DREAM subunits and cyclin/CDK complexes. p107 is one of the major partners of B55α, which also associates with pRB in RCS cells. FGF1 induces dephosphorylation of p107, its translocation to the nucleus, remodeling of p107 complexes, and enhances its interaction with E2F4 and …
author: Kurimchak, Alison
language: eng
keywords: Biology, Molecular, B55alpha, Cell Cycle, Fgf1, P107, Pp2a
license: http://rightsstatements.org/vocab/InC/1.0/
date published: 2014
date modified: 2026-07-27T21:20:39Z
provider: Temple University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Temple University. Libraries

PropertyValue
property ID: Handle
value: http://hdl.handle.net/20.500.12613/3150