NEW SMALL RNA BIOGENESIS PROTEINS IN PARASITE PLATYHELMINTHS

MALDONADO, L.; FOX, A.; MACCHIAROLI, N.; FONTENLA, S.; CUCHER, M.; TORT, J.; ROSENZVIT, M.; KAMENETZKY, L.

Congreso; X-Meeting & BSB; 2013

Background: small RNAs including microRNAs (miRNAs), small interfering-RNAs(siRNAs) and piwi-RNAs (piRNAs) control several pathways such as developmental timing,hematopoiesis, organogenesis, apoptosis, cell proliferation and tumorigenesis.Canonical animal miRNAs are generated from long hairpin precursors which are processedby three principal proteins: Dicer, DGCR8 (Pasha) and Drosha. The resulting mature miRNA isloaded onto the effector protein Argonaute (Ago). The miRNA-Ago complex is guided by theloaded miRNA to specifically interact with the target mRNA. This interaction produces theinhibition of the target protein expression by ?slicing?, destabilization or translation inhibition of thetarget mRNA.Argonaute proteins are evolutionarily conserved and can be phylogenetically subdivided intothe Ago and Piwi subfamily. Ago proteins are ubiquitously expressed and bind to siRNAs ormiRNAs but Piwi proteins expression is mostly restricted to germ line and associate with piRNAsto facilitate silencing of mobile genetic elements.With the aim to identify the main small RNA pathway proteins in Platyhelminth parasiteswe searched for Ago, Piwi, Dicer, Pasha and Drosha proteins in recently generated Echinococcusgenomes and transcriptomes.Results: We found Ago, Dicer, Pasha and Drosha orthologs expressed in both Echinococcusgranulosus and Echinococcus multilocularis. Interestingly, phylogenetic analysis showed newAgo/Piwi-like proteins divergent from those described in humans, mice and flies. We confirmed theexpression of these new proteins by RT-qPCR from metacestodes, the clinical relevant stage of thehydatid disease. In order to identify conserved domains and the possible interaction betweenmiRNA and specific protein domains, we have also modelled the Ago/Piwi-like proteins bycomparative modeling with Swissmodel and Pymol softwares. The structural analysis confirmed thenew protein clade.Conclusions: Computational analyses including phylogenetic and protein structure studies suggestthe existence of new Ago/Piwi-like proteins in Echinococcus spp. containing conserved structuraldomains described to be involved in binding miRNAs. Interestingly, in contrast to mammals, inwhich some Agos do not have the core related to slicer activity, we have found the ?DEDH? core inall analyzed proteins; which suggests that these proteins not only could bind small RNAs but alsothey could have slicer activity. In spite of overall domain conservation, some particular residues aredivergent between canonical and platyhelminth Ago/Piwi proteins and are under evaluation. Datagenerated in this work will be integrated into FlatDB database which is under development bycollaborative effort of Brazil-Argentina-Uruguay research centres for accessing omics data forparasitic PlatyhelminthesSupported by: ANPCyT-CABBIO 3044, CAPG 070/13, CONICET