RNAi and miRNA pathways in Annelids and Molluscs

Abstract

RNA silencing denotes sequence-specific repression mediated by small RNAs. In metazoa, there are two mechanistically closely related pathways: RNA interference (RNAi) and microRNA (miRNA) pathway. The miRNA pathway regulates endogenous protein-coding gene expression and has been implicated in many biological processes. RNAi generally serves as a form of innate immunity targeting viruses and mobile elements. This review is summarizing information about RNAi and miRNA pathways in protostome phyla: Annelida and Mollusca. The molecular mechanisms of dsRNA and miRNA pathways in annelids remain largely unexplored. The available information points towards coexistence of miRNA and RNAi pathways, however, their integration or genetic separation remain unclear. Molluscs are an interesting taxon, which appears to have a unique setup of RNA silencing possibly employing a single Argonaute protein while it also employs interferon-like pathway elements.