Renaissance of mammalian endogenous RNAi

RNA interference (RNAi) denotes sequence-specific mRNA degradation induced by long double-stranded RNA (dsRNA). RNAi is an ancient eukaryotic defense mechanism against viruses and mobile elements. In mammals, endogenous RNAi was outstripped during evolution by the current innate and acquired immunity. The RNAi apparatus, which remains essentially intact, serves mostly the microRNA pathway, which regulates endogenous gene expression. Remarkably, several recent publications brought the mammalian endogenous RNAi pathway back into the spotlight. Here, I will provide an up-to-date review of the mammalian endogenous RNAi pathway with a focus on its defensive role and overlaps with miRNA and piRNA pathways.