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Multiple protein-protein interactions by RNA polymerase I-associated factor PAF49 and role of PAF49 in rRNA

Kazuo Yamamoto1, Mika Yamamoto, Ken-ichi Hanada

  • 1Department of Biochemistry, Saitama Medical School, Iruma-gun, Japan.

Molecular and Cellular Biology
|July 1, 2004
PubMed

Insights

We identified PAF49, a novel RNA polymerase I-associated factor, crucial for ribosomal RNA (rRNA) transcription. This factor interacts with PAF53 and SL1, and its function is essential for rRNA synthesis in cells.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • RNA polymerase I (Pol I) is essential for ribosomal RNA (rRNA) synthesis.
  • PAF53 was previously identified as a critical factor associated with Pol I in mammalian rRNA transcription.

Purpose of the Study:

  • To isolate and characterize a novel Pol I-associated factor, PAF49.
  • To elucidate the role of PAF49 in rRNA transcription and its interactions with other transcription factors.

Main Methods:

  • Copurification of PAF49 with Pol I.
  • Coimmunoprecipitation assays to confirm physical interactions.
  • In vitro transcription assays using anti-PAF49 antibodies.
  • In vivo studies involving overexpression of PAF49 deletion mutants.
  • Immunolocalization to determine cellular localization of PAF49.

Main Results:

  • PAF49 was identified as a Pol I-associated factor, homologous to human ASE-1.
  • PAF49 interacts with PAF53 and the selectivity factor SL1 (including TAF(I)48).
  • Antibodies against PAF49 inhibited rRNA transcription in vitro, and this inhibition was reversible.
  • Overexpression of a PAF49 deletion mutant reduced pre-rRNA synthesis in vivo.
  • PAF49 localizes to the nucleolus in growing cells and disperses in growth-arrested cells.

Conclusions:

  • PAF49/ASE-1 is a crucial component of the Pol I transcription machinery.
  • PAF49 plays a significant role in regulating rRNA synthesis.
  • The interactions of PAF49 with PAF53 and SL1 are important for its function in rRNA transcription.

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