Argonaute proteins: key players in RNA silencing

Abstract

The Argonautes represent a highly conserved gene family that is found in almost all eukaryotes and is even found in bacteria and archaea. Many members of the Argonaute gene family are found in the genomes of plants and animals, with an exceptional representation in the nematode Caenorhabditis elegans, which has at least 26 Argonaute genes. Argonaute proteins contain four conserved domains: the N-terminal, PAZ (which is responsible for small RNA binding), Mid and PIWI (which confers catalytic activities) domains. Argonaute proteins associate with small non-coding RNAs (such as small interfering (si)RNAs and microRNAs (miRNAs)) and function in RNA-based silencing mechanisms by altering protein synthesis and affecting RNA stability. Argonaute proteins also contribute to the maintenance of chromosome integrity, are involved in siRNA and miRNA maturation and can even participate in the production of a new class of small non-coding RNAs known as Piwi-interacting (pi)RNAs.