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mRNA maturation in giant viruses: variation on a theme.

Priet S, Lartigue A, Debart F, Claverie JM, Abergel C - Nucleic Acids Res. (2015)

Bottom Line: Unexpectedly, the vPAPs are homodimeric and uniquely self-processive.The vPAP backbone structures exhibit a symmetrical architecture with two subdomains sharing a nucleotidyltransferase topology, suggesting that vPAPs originate from an ancestral duplication.A Poxvirus processivity factor homologue encoded by Megavirus chilensis displays a conserved 5'-GpppA 2'O methyltransferase activity but is also able to internally methylate the mRNAs' polyA tails.

View Article: PubMed Central - PubMed

Affiliation: Architecture et Fonction des Macromolécules Biologiques, CNRS UMR 7257, Aix-Marseille Université, 163 Avenue de Luminy, Case 932, 13288 Marseille cedex 9, France.

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Electrostatic surface representation of the Mg561 protein. (A) Electrostatic surface of the Mg561 dimer. The green lines correspond to the possible RNA binding sites in the positively charged grooves (blue). The green arrows point the position of the second tunnel and the dashed lines delineate the tunnel path under the surface. Contour levels: red, V < −10 kcal/mol; white, −10 kcal/mol < V < +10 kcal/mol; blue, V > +10 kcal/mol. (B) Proposed mimiviruses PAP RNA and ATP binding mode (left panel, Mg561 monomer) based on the superimposition of the VP55 complex with ATP and RNA (PDB 3ERC) on Mg561 (right panel). Predicted cation sites are marked as green balls. (C) As in (B) but with the Mg561 dimer (left panel). Close-up of the central tunnel (right panel). (D) Proposed ATP entry route pointed by the green arrow (left panel). Close-up of the tunnel through the ATP binding site (right panel).
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Figure 5: Electrostatic surface representation of the Mg561 protein. (A) Electrostatic surface of the Mg561 dimer. The green lines correspond to the possible RNA binding sites in the positively charged grooves (blue). The green arrows point the position of the second tunnel and the dashed lines delineate the tunnel path under the surface. Contour levels: red, V < −10 kcal/mol; white, −10 kcal/mol < V < +10 kcal/mol; blue, V > +10 kcal/mol. (B) Proposed mimiviruses PAP RNA and ATP binding mode (left panel, Mg561 monomer) based on the superimposition of the VP55 complex with ATP and RNA (PDB 3ERC) on Mg561 (right panel). Predicted cation sites are marked as green balls. (C) As in (B) but with the Mg561 dimer (left panel). Close-up of the central tunnel (right panel). (D) Proposed ATP entry route pointed by the green arrow (left panel). Close-up of the tunnel through the ATP binding site (right panel).

Mentions: The second domain (D2) exhibits the typical topology of a nucleotidyltransferase (NT) domain made of a mixed five-stranded β sheet and two connecting helices and, as for the VP55 structure, the two helices pack against one side of the β sheet parallel to the β strands (Figures 1B and 3). The canonical acidic residues D94-E96-D143 are properly positioned and ordered in the crystal structure as evidenced by the 2Fo-Fc electron density maps contoured at 1σ on the of M. chilensis and Mimivirus PAP active sites (Supplementary Figure S6A). A water molecule replacing the Mg2+ ion usually found in structures in complex with ATP is used to help locate the active sites in the figures (Figures 3 and 5B, Supplementary Figure S4). The helix-turn motif within the β sheet presents a 10-residues longer loop relative to the Vaccinia virus PAP structure. This loop stabilizes the α1 helix of the same monomer in an orientation perpendicular to D2. This domain thus appears equivalent to the catalytic domain of VP55 made of an NT domain extended by one helix (Mg561 α5, VP55 α12), two antiparallel strands (β6-β7) and terminated by two parallel helices (Mg561 α6-α7, VP55 α13-α15). This topology thus defines the catalytic domain of viral PAPs (Figure 1B).


mRNA maturation in giant viruses: variation on a theme.

Priet S, Lartigue A, Debart F, Claverie JM, Abergel C - Nucleic Acids Res. (2015)

Electrostatic surface representation of the Mg561 protein. (A) Electrostatic surface of the Mg561 dimer. The green lines correspond to the possible RNA binding sites in the positively charged grooves (blue). The green arrows point the position of the second tunnel and the dashed lines delineate the tunnel path under the surface. Contour levels: red, V < −10 kcal/mol; white, −10 kcal/mol < V < +10 kcal/mol; blue, V > +10 kcal/mol. (B) Proposed mimiviruses PAP RNA and ATP binding mode (left panel, Mg561 monomer) based on the superimposition of the VP55 complex with ATP and RNA (PDB 3ERC) on Mg561 (right panel). Predicted cation sites are marked as green balls. (C) As in (B) but with the Mg561 dimer (left panel). Close-up of the central tunnel (right panel). (D) Proposed ATP entry route pointed by the green arrow (left panel). Close-up of the tunnel through the ATP binding site (right panel).
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Related In: Results  -  Collection

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Figure 5: Electrostatic surface representation of the Mg561 protein. (A) Electrostatic surface of the Mg561 dimer. The green lines correspond to the possible RNA binding sites in the positively charged grooves (blue). The green arrows point the position of the second tunnel and the dashed lines delineate the tunnel path under the surface. Contour levels: red, V < −10 kcal/mol; white, −10 kcal/mol < V < +10 kcal/mol; blue, V > +10 kcal/mol. (B) Proposed mimiviruses PAP RNA and ATP binding mode (left panel, Mg561 monomer) based on the superimposition of the VP55 complex with ATP and RNA (PDB 3ERC) on Mg561 (right panel). Predicted cation sites are marked as green balls. (C) As in (B) but with the Mg561 dimer (left panel). Close-up of the central tunnel (right panel). (D) Proposed ATP entry route pointed by the green arrow (left panel). Close-up of the tunnel through the ATP binding site (right panel).
Mentions: The second domain (D2) exhibits the typical topology of a nucleotidyltransferase (NT) domain made of a mixed five-stranded β sheet and two connecting helices and, as for the VP55 structure, the two helices pack against one side of the β sheet parallel to the β strands (Figures 1B and 3). The canonical acidic residues D94-E96-D143 are properly positioned and ordered in the crystal structure as evidenced by the 2Fo-Fc electron density maps contoured at 1σ on the of M. chilensis and Mimivirus PAP active sites (Supplementary Figure S6A). A water molecule replacing the Mg2+ ion usually found in structures in complex with ATP is used to help locate the active sites in the figures (Figures 3 and 5B, Supplementary Figure S4). The helix-turn motif within the β sheet presents a 10-residues longer loop relative to the Vaccinia virus PAP structure. This loop stabilizes the α1 helix of the same monomer in an orientation perpendicular to D2. This domain thus appears equivalent to the catalytic domain of VP55 made of an NT domain extended by one helix (Mg561 α5, VP55 α12), two antiparallel strands (β6-β7) and terminated by two parallel helices (Mg561 α6-α7, VP55 α13-α15). This topology thus defines the catalytic domain of viral PAPs (Figure 1B).

Bottom Line: Unexpectedly, the vPAPs are homodimeric and uniquely self-processive.The vPAP backbone structures exhibit a symmetrical architecture with two subdomains sharing a nucleotidyltransferase topology, suggesting that vPAPs originate from an ancestral duplication.A Poxvirus processivity factor homologue encoded by Megavirus chilensis displays a conserved 5'-GpppA 2'O methyltransferase activity but is also able to internally methylate the mRNAs' polyA tails.

View Article: PubMed Central - PubMed

Affiliation: Architecture et Fonction des Macromolécules Biologiques, CNRS UMR 7257, Aix-Marseille Université, 163 Avenue de Luminy, Case 932, 13288 Marseille cedex 9, France.

Show MeSH
Related in: MedlinePlus