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MPP6 is an exosome-associated RNA-binding protein involved in 5.8S rRNA maturation

Geurt Schilders1, Reinout Raijmakers, Jos M H Raats

  • 1Department of Biochemistry, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands.

Nucleic Acids Research
|January 7, 2006
PubMed

Insights

M-phase phosphoprotein 6 (MPP6) is a nucleolar protein that recruits the exosome complex to pre-ribosomal RNA (pre-rRNA). This interaction is crucial for the maturation of 5.8S ribosomal RNA (rRNA).

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The exosome complex, a 3'-->5' exoribonuclease, plays a vital role in RNA metabolism.
  • Specific proteins are thought to recruit the exosome to target RNAs for regulated processing.
  • M-phase phosphoprotein 6 (MPP6) has been previously identified as a co-purifying protein with the human exosome.

Purpose of the Study:

  • To investigate the function and localization of M-phase phosphoprotein 6 (MPP6) in relation to the exosome complex.
  • To determine MPP6's role in RNA processing, specifically in the context of the nucleolus and rRNA maturation.

Main Methods:

  • Co-immunoprecipitation and biochemical fractionation to assess protein-exosome association.
  • Subcellular localization studies using HEp-2 cells to determine MPP6 accumulation sites.
  • siRNA-mediated knock-down experiments to evaluate MPP6's function in rRNA processing.
  • In vitro RNA-binding assays to characterize MPP6's interaction with RNA sequences.

Main Results:

  • MPP6 was found to accumulate in the nucleoli of HEp-2 cells.
  • MPP6 associates with a subset of nuclear exosome components.
  • MPP6 is essential for the generation of the 3' end of 5.8S ribosomal RNA (rRNA).
  • MPP6 exhibits in vitro RNA-binding activity, preferring pyrimidine-rich sequences and binding to the ITS2 element of pre-rRNAs.

Conclusions:

  • MPP6 functions as a nucleolus-specific co-factor for the exosome.
  • MPP6 is required for the efficient recruitment of the exosome to pre-ribosomal RNA.
  • MPP6 plays a critical role in the maturation of 5.8S rRNA.

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