TAF4 inactivation reveals the 3 dimensional growth promoting activities of collagen 6A3

PLoS One. 2014 Feb 3;9(2):e87365. doi: 10.1371/journal.pone.0087365. eCollection 2014.

Abstract

Collagen 6A3 (Col6a3), a component of extracellular matrix, is often up-regulated in tumours and is believed to play a pro-oncogenic role. However the mechanisms of its tumorigenic activity are poorly understood. We show here that Col6a3 is highly expressed in densely growing mouse embryonic fibroblasts (MEFs). In MEFs where the TAF4 subunit of general transcription factor IID (TFIID) has been inactivated, elevated Col6a3 expression prevents contact inhibition promoting their 3 dimensional growth as foci and fibrospheres. Analyses of gene expression in densely growing Taf4(-/-) MEFs revealed repression of the Hippo pathway and activation of Wnt signalling. The Hippo activator Kibra/Wwc1 is repressed under dense conditions in Taf4(-/-) MEFs, leading to nuclear accumulation of the proliferation factor YAP1 in the cells forming 3D foci. At the same time, Wnt9a is activated and the Sfrp2 antagonist of Wnt signalling is repressed. Surprisingly, treatment of Taf4(-/-) MEFs with all-trans retinoic acid (ATRA) restores contact inhibition suppressing 3D growth. ATRA represses Col6a3 expression independently of TAF4 expression and Col6a3 silencing is sufficient to restore contact inhibition in Taf4(-/-) MEFs and to suppress 3D growth by reactivating Kibra expression to induce Hippo signalling and by inducing Sfrp2 expression to antagonize Wnt signalling. All together, these results reveal a critical role for Col6a3 in regulating both Hippo and Wnt signalling to promote 3D growth, and show that the TFIID subunit TAF4 is essential to restrain the growth promoting properties of Col6a3. Our data provide new insight into the role of extra cellular matrix components in regulating cell growth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Blotting, Western
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Adhesion / drug effects
  • Cell Adhesion / genetics
  • Cell Cycle Proteins
  • Cell Proliferation*
  • Cells, Cultured
  • Collagen Type VI / genetics
  • Collagen Type VI / metabolism*
  • Embryo, Mammalian / cytology
  • Fibroblasts / cytology
  • Fibroblasts / metabolism*
  • Gene Expression
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Knockout
  • Microscopy, Confocal
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA Interference
  • Reverse Transcriptase Polymerase Chain Reaction
  • Spheroids, Cellular / cytology
  • Spheroids, Cellular / drug effects
  • Spheroids, Cellular / metabolism
  • Transcription Factor TFIID / genetics
  • Transcription Factor TFIID / metabolism*
  • Tretinoin / pharmacology
  • Wnt Signaling Pathway / drug effects
  • Wnt Signaling Pathway / genetics

Substances

  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Cell Cycle Proteins
  • Collagen Type VI
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Phosphoproteins
  • Sfrp2 protein, mouse
  • TAF4 protein, mouse
  • Transcription Factor TFIID
  • Wwc1 protein, mouse
  • Yap1 protein, mouse
  • Tretinoin
  • Hippo protein, mouse
  • Protein-Serine-Threonine Kinases

Grant support

This work was supported by grants from the CNRS, the INSERM, the Association pour la Recherche contre le Cancer, the Ligue Nationale et Départementale Région Alsace contre le Cancer and in Institut National du Cancer (INCa). ID is an ‘équipe labellisée’ of the Ligue Nationale contre le Cancer. EC was supported by a fellowship from the Fondation pour la Recherche Medicale. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.