Phenotypic transcription factors epigenetically mediate cell growth control

Area of Science:

• Molecular Biology
• Developmental Biology
• Cell Biology

Background:

• Ribosomal RNA (rRNA) gene expression is downregulated during cell differentiation processes like osteogenesis, myogenesis, and adipogenesis.
• Understanding the mechanisms linking growth control and cell fate commitment is crucial.

Purpose of the Study:

• To investigate how cell fate-determining factors regulate rRNA gene expression during lineage progression.
• To elucidate the interplay between growth control and phenotype commitment.

Main Methods:

• Chromatin immunoprecipitation to assess factor occupancy at rDNA loci.
• RNA interference and ectopic expression studies to determine functional roles.
• Analysis of interactions with upstream binding factor (UBF-1) at nucleoli.

Main Results:

• Cell fate factors (MyoD, myogenin, Runx2, C/EBPbeta) bind to rDNA loci and suppress rRNA expression.
• This suppression is accompanied by decreased rRNA expression and reduced occupancy by c-Myc.
• Phenotypic factors interact with UBF-1, an interaction maintained epigenetically on mitotic chromosomes.

Conclusions:

• Lineage-specific differentiation factors epigenetically control ribosomal biogenesis.
• This mechanism coordinates cell growth with phenotype commitment during development.
• Suppression of rRNA genes and protein synthesis by differentiation factors is a general developmental mechanism.