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Crystal structure of the RRM domain of poly(A)-specific ribonuclease reveals a novel m(7)G-cap-binding mode

Thomas Monecke1, Stephanie Schell, Achim Dickmanns

  • 1Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, GZMB, Georg-August-Universität Göttingen, 37077 Göttingen, Germany.

Journal of Molecular Biology
|August 13, 2008
PubMed

Insights

Poly(A)-specific ribonuclease (PARN) binds both mRNA ends. Its RRM domain structure reveals a novel 7-methylguanosine cap binding mode, enhancing deadenylation activity.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Poly(A)-specific ribonuclease (PARN) is a key enzyme in eukaryotic mRNA decay.
  • PARN binds both the 3' poly(A) tail and the 5' 7-methylguanosine (m7G) cap of mRNAs.
  • PARN's interaction with the m7G cap stimulates deadenylation and enhances processivity.

Purpose of the Study:

  • To determine the crystal structure of the PARN-RRM domain bound to m7G triphosphate.
  • To elucidate the novel binding mode of the m7G cap by the PARN-RRM domain.
  • To investigate the structural basis for PARN's interaction with mRNA 5' ends.

Main Methods:

  • X-ray crystallography was used to determine the structure of the PARN-RRM domain.
  • The PARN-RRM domain was crystallized in complex with m7G triphosphate.
  • Structural analysis focused on the m7G binding pocket and RRM domain conformation.

Main Results:

  • The crystal structure revealed a novel binding mode for the m7G cap by the PARN-RRM domain.
  • The m7G binding pocket is located outside the canonical RNA-binding surface of the RRM domain.
  • The PARN-RRM domain exhibits significant conformational flexibility, including alpha-helix exchange.

Conclusions:

  • PARN utilizes a unique mechanism for m7G cap binding, distinct from other cap-binding proteins.
  • The structural flexibility of the PARN-RRM domain likely contributes to its functional versatility.
  • Understanding PARN's interaction with the m7G cap provides insights into mRNA regulation and decay pathways.

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