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c-Jun supports ribosomal RNA processing and nucleolar localization of RNA helicase DDX21

Tim H Holmström1, Antoine Mialon, Marko Kallio

  • 1Centre for Biotechnology, University of Turku and Abo Akademi University, 20520 Turku, Finland.

The Journal of Biological Chemistry
|January 9, 2008
PubMed

Insights

The transcription factor c-Jun regulates cell behavior through non-transcriptional mechanisms. It controls rRNA processing and DDX21 protein localization within the nucleolus.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Gene Regulation

Background:

  • The transcription factor c-Jun (AP-1) is known for regulating gene expression.
  • Emerging evidence suggests c-Jun also influences cell behavior via non-transcriptional pathways.
  • The precise non-transcriptional roles of c-Jun remain largely unelucidated.

Purpose of the Study:

  • To investigate the non-transcriptional mechanisms of c-Jun.
  • To determine c-Jun's role in ribosomal RNA (rRNA) processing.
  • To explore c-Jun's interaction with RNA helicase DDX21.

Main Methods:

  • Small interfering RNA (siRNA) was used to deplete c-Jun in mammalian cells.
  • Cellular localization of DDX21 was assessed using microscopy.
  • rRNA accumulation and DDX21 binding were quantified.
  • Exogenous c-Jun expression was used to rescue phenotypes.

Main Results:

  • c-Jun depletion inhibited 28S and 18S rRNA accumulation.
  • c-Jun depletion caused DDX21 to translocate from the nucleolus to the nucleoplasm.
  • Exogenous c-Jun expression rescued DDX21 translocation and restored rRNA binding.
  • Direct interaction between c-Jun and DDX21 was shown to regulate DDX21 nucleolar localization.

Conclusions:

  • c-Jun plays a crucial role in rRNA processing and DDX21 nucleolar localization.
  • A novel nucleolar mechanism for c-Jun-mediated regulation of cell behavior is identified.
  • Observed phenotypes in c-Jun-depleted models may be partly attributed to impaired rRNA processing.

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