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The conserved eukaryotic Pan2-Pan3 deadenylation complex shortens cytoplasmic mRNA 3' polyA tails to regulate mRNA stability. Although the exonuclease activity resides in Pan2, efficient deadenylation requires Pan3. The mechanistic role of Pan3 is unclear. Here, we show that Pan3 binds RNA directly both through its pseudokinase/C-terminal domain and via an N-terminal zinc finger that binds polyA RNA specifically. In contrast, isolated Pan2 is unable to bind RNA. Pan3 binds to the region of Pan2 that links its N-terminal WD40 domain to the C-terminal part that contains the exonuclease, with a 2:1 stoichiometry. The crystal structure of the Pan2 linker region bound to a Pan3 homodimer shows how the unusual structural asymmetry of the Pan3 dimer is used to form an extensive high-affinity interaction. This binding allows Pan3 to supply Pan2 with substrate polyA RNA, facilitating efficient mRNA deadenylation by the intact Pan2-Pan3 complex.

Original publication

DOI

10.15252/embj.201488373

Type

Journal article

Journal

EMBO J

Publication Date

17/07/2014

Volume

33

Pages

1514 - 1526

Keywords

Pan2–Pan3, gene expression, mRNA deadenylation, polyA tail, protein structure, Base Sequence, Chaetomium, Chromatography, Affinity, Cloning, Molecular, Electrophoretic Mobility Shift Assay, Exoribonucleases, Magnetic Resonance Spectroscopy, Mass Spectrometry, Models, Molecular, Molecular Sequence Data, Multiprotein Complexes, Poly(A)-Binding Proteins, Protein Binding, Protein Multimerization, RNA, Messenger, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sepharose, Sequence Analysis, DNA