Argonaute proteins are active throughout the lifetime in a variety of organisms and they bind to small RNAs (sRNAs) to regulate gene expression. The Argonaute proteins of vertebrates can be classified into two clades: the Ago clade and the Piwi clade. Both clades have N, L1, L2, PAZ, MID and PIWI domains. The N domain is involved in the loading of sRNAs. L1 and L2 domains facilitate the linking between domains. The PAZ and MID domains exert functions by anchoring sRNAs. The PIWI domain of some Argonaute proteins has RNase H-like structure and exerts the endonuclease function. Ago proteins regulate gene expression at transcriptional and post-transcriptional levels. Piwi proteins mainly exist in the germ cells, silencing transposons in different ways to keep genome integrality and regulating gene expression. In recent years, great progress has been made in Argonaute proteins in terms of the crystal structures, functions, and expression patterns. By reviewing the relevant studies, we elaborate on the structures, sRNA dependence, gene expression regulation, and biological roles of the Ago and Piwi proteins in vertebrates, aiming to clarify the roles of Argonaute proteins in epigenetic regulation and provide a reference for further research and application of these proteins.
Argonaute Proteins/chemistry* ; Animals ; Vertebrates/metabolism* ; Gene Expression Regulation ; RNA, Small Interfering/metabolism* ; Epigenesis, Genetic ; Humans