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Coordinated decreases in rRNA gene transcription factors and rRNA synthesis during muscle cell differentiation

D E Larson1, W Xie, M Glibetic

  • 1Department of Molecular Biology and Genetics, University of Guelph, ON, Canada.

Proceedings of the National Academy of Sciences of the United States of America
|September 1, 1993
PubMed

Insights

During muscle cell differentiation, ribosomal RNA (rRNA) synthesis and transcription factors like upstream binding factors (UBF) significantly decrease. This regulation involves multiple pathways beyond acute responses.

Area of Science:

  • Molecular Biology
  • Cellular Differentiation
  • Gene Regulation

Background:

  • Ribosomal RNA (rRNA) synthesis is crucial for cell growth and protein production.
  • Cellular differentiation, such as myogenesis, involves complex gene expression changes.
  • Regulation of rRNA synthesis is vital for adapting cellular function to physiological demands.

Purpose of the Study:

  • To investigate the molecular mechanisms regulating rRNA synthesis during L6 myoblast differentiation.
  • To identify key transcription factors involved in the downregulation of rRNA gene transcription.
  • To elucidate the role of upstream binding factors (UBF) in this process.

Main Methods:

  • Nuclear run-on assays to measure rRNA gene transcription rates.
  • Immunoblot analysis to quantify protein levels of transcription factors.
  • RNA blot analysis to assess mRNA levels of key regulatory proteins.

Main Results:

  • rRNA synthesis and transcription rates significantly decrease during myoblast differentiation.
  • Levels of RNA polymerase I transcription factors, UBF1 and UBF2, are markedly reduced.
  • Downregulation of UBF mRNA precedes the decrease in UBF protein, indicating transcriptional control.

Conclusions:

  • Regulation of rRNA gene transcription during differentiation involves decreased levels of UBF transcription factors.
  • The decline in UBF is specific and not due to general protein degradation, as evidenced by myosin accumulation.
  • Physiological processes like differentiation may utilize multiple regulatory pathways for rRNA gene transcription control.

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