Dataset Information

Crystal structure of the MID-PIWI lobe of a eukaryotic Argonaute protein.

ABSTRACT: Argonaute proteins (AGOs) are essential effectors in RNA-mediated gene silencing pathways. They are characterized by a bilobal architecture, in which one lobe contains the N-terminal and PAZ domains and the other contains the MID and PIWI domains. Here, we present the first crystal structure of the MID-PIWI lobe from a eukaryotic AGO, the Neurospora crassa QDE-2 protein. Compared to prokaryotic AGOs, the domain orientation is conserved, indicating a conserved mode of nucleic acid binding. The PIWI domain shows an adaptable surface loop next to a eukaryote-specific ?-helical insertion, which are both likely to contact the PAZ domain in a conformation-dependent manner to sense the functional state of the protein. The MID-PIWI interface is hydrophilic and buries residues that were previously thought to participate directly in the allosteric regulation of guide RNA binding. The interface includes the binding pocket for the guide RNA 5' end, and residues from both domains contribute to binding. Accordingly, micro-RNA (miRNA) binding is particularly sensitive to alteration in the MID-PIWI interface in Drosophila melanogaster AGO1 in vivo. The structure of the QDE-2 MID-PIWI lobe provides molecular and mechanistic insight into eukaryotic AGOs and has significant implications for understanding the role of these proteins in silencing.

SUBMITTER: Boland A

PROVIDER: S-EPMC3127882 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Crystal structure of the MID-PIWI lobe of a eukaryotic Argonaute protein.

Boland Andreas A Huntzinger Eric E Schmidt Steffen S Izaurralde Elisa E Weichenrieder Oliver O

Proceedings of the National Academy of Sciences of the United States of America 20110606 26

Argonaute proteins (AGOs) are essential effectors in RNA-mediated gene silencing pathways. They are characterized by a bilobal architecture, in which one lobe contains the N-terminal and PAZ domains and the other contains the MID and PIWI domains. Here, we present the first crystal structure of the MID-PIWI lobe from a eukaryotic AGO, the Neurospora crassa QDE-2 protein. Compared to prokaryotic AGOs, the domain orientation is conserved, indicating a conserved mode of nucleic acid binding. The PI ...[more]

PMID: 21646546

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Project description:Platyhelminthes comprise one of the major phyla of invertebrate animals, inhabiting a wide range of ecosystems, and one of the most successful in adapting to parasitic life. Small non-coding RNAs have been implicated in regulating complex developmental transitions in model parasitic species. Notably, parasitic flatworms have lost Piwi RNA pathways but gained a novel Argonaute gene. Herein, we analyzed, contrasted and compared the conservation of small RNA pathways among several free-living species (a paraphyletic group traditionally known as 'turbellarians') and parasitic species (organized in the monophyletic clade Neodermata) to disentangle possible adaptations during the transition to parasitism. Our findings showed that complete miRNA and RNAi pathways are present in all analyzed free-living flatworms. Remarkably, whilst all 'turbellarians' have Piwi proteins, these were lost in parasitic Neodermantans. Moreover, two clusters of Piwi class Argonaute genes are present in all 'turbellarians'. Interestingly, we identified a divergent Piwi class Argonaute in free living flatworms exclusively, which we named 'Fliwi'. In addition, other key proteins of the Piwi pathways were conserved in 'turbellarians', while none of them were detected in Neodermatans. Besides Piwi and the canonical Argonaute proteins, a flatworm-specific class of Argonautes (FL-Ago) was identified in the analyzed species confirming its ancestrallity to all Platyhelminthes. Remarkably, this clade was expanded in parasitic Neodermatans, but not in free-living species. These phyla-specific Argonautes showed lower sequence conservation compared to other Argonaute proteins, suggesting that they might have been subjected to high evolutionary rates. However, key residues involved in the interaction with the small RNA and mRNA cleavage in the canonical Argonautes were more conserved in the FL-Agos than in the Piwi Argonautes. Whether this is related to specialized functions and adaptations to parasitism in Neodermatans remains unclear. In conclusion, differences detected in gene conservation, sequence and structure of the Argonaute family suggest tentative biological and evolutionary diversifications that are unique to Platyhelminthes. The remarkable divergencies in the small RNA pathways between free-living and parasitic flatworms indicate that they may have been involved in the adaptation to parasitism of Neodermatans.

Dataset Information

Crystal structure of the MID-PIWI lobe of a eukaryotic Argonaute protein.

Publications

Crystal structure of the MID-PIWI lobe of a eukaryotic Argonaute protein.

Similar Datasets

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