Activation of the retinoblastoma gene expression by Bcl-3: Implication for muscle cell differentiation

Yuzuru Shiio, Jun Ichi Sawada, Hiroshi Handa, Tadashi Yamamoto, Jun Ichiro Inoue

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


The retinoblastoma (Rb) protein is a master regulator of cell cycle. Accumulating evidence suggests that elevation of Rb expression is a key event in differentiation of various cell types. However the mechanism of regulation of Rb expression is poorly understood. Here we report that the candidate oncoprotein Bcl-3, previously characterized as a member of the IκB family, activates transcription of the Rb gene, whose promoter has no typical κB sites. A target element for Bcl-3 that matches the consensus for the E4TF1/GABP transcription factor was identified. Bcl-3 was shown to promote tetramer formation of E4TF1. During muscle cell differentiation, increased bcl-3 expression was observed before the induction of the Rb mRNA. Transient expression of Bcl-3 in myoblasts was shown to induce expression of the endogenous Rb. Furthermore, expression of the antisense bcl-3 RNA in myoblasts suppressed induction of Rb and myogenic differentiation. These results suggest that Bcl-3 is an upstream regulator of Rb expression during differentiation of muscle cells.

Original languageEnglish (US)
Pages (from-to)1837-1845
Number of pages9
Issue number9
StatePublished - 1996


  • Bcl-3
  • E4TF1
  • GABP
  • Muscle differentiation
  • Rb

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research


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