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mRNA maturation in giant viruses: variation on a theme
Stéphane Priet1, Audrey Lartigue2, Françoise Debart3
1Architecture et Fonction des Macromolécules Biologiques, CNRS UMR 7257, Aix-Marseille Université, 163 Avenue de Luminy, Case 932, 13288 Marseille cedex 9, France.
Nucleic Acids Research
|March 18, 2015
Summary
Mimiviridae giant viruses use unique hairpin cleavage and viral polyA polymerases (vPAPs) for mRNA processing. These self-processive vPAPs and a Poxvirus homologue reveal novel viral gene expression strategies.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Giant viruses, such as those in the Mimiviridae family, replicate within the host cell's cytoplasm.
- Viral gene transcription in these viruses relies on a dedicated viral transcription apparatus.
- Unique mRNA polyadenylation in Mimiviridae occurs at hairpin-forming palindromic sequences.
Purpose of the Study:
- To identify the enzyme responsible for hairpin cleavage and viral polyA polymerases (vPAPs) in Mimiviridae.
- To characterize the structure and function of these viral enzymes.
- To understand the mechanism of mRNA processing and its implications for viral gene expression.
Main Methods:
- Analysis of a conserved gene cluster encoding hairpin cleavage enzyme and vPAPs.
- Biochemical assays to determine vPAP self-processivity and enzyme activity.
- Structural analysis of vPAP backbone and Poxvirus processivity factor homologue.
Main Results:
- A conserved gene cluster encodes both hairpin cleavage enzyme and homodimeric, self-processive vPAPs.
- vPAP structures reveal a symmetrical architecture with two subdomains, suggesting ancestral duplication.
- A Megavirus chilensis Poxvirus homologue exhibits methyltransferase activity and internal mRNA polyA tail methylation.
Conclusions:
- Mimiviridae employs a unique enzymatic system for mRNA polyadenylation via hairpin cleavage and self-processive vPAPs.
- The structural and functional characteristics of vPAPs suggest an evolutionary origin from gene duplication.
- These findings illuminate the intricate strategies Mimiviridae viruses use to manipulate host translation machinery.
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