title: The Piwi-piRNA pathway provides an adaptive defense in the transposon arms race.
abstract: Increasingly complex networks of small RNAs act through RNA-interference (RNAi) pathways to regulate gene expression, to mediate antiviral responses, to organize chromosomal domains, and to restrain the spread of selfish genetic elements. Historically, RNAi has been defined as a response to double-stranded RNA. However, some small RNA species may not arise from double-stranded RNA precursors. Yet, like microRNAs and small interfering RNAs, such species guide Argonaute proteins to silencing targets through complementary base-pairing. Silencing can be achieved by corecruitment of accessory factors or through the activity of Argonaute itself, which often has endonucleolytic activity. As a specific and adaptive regulatory system, RNAi is used throughout eukarya, which indicates a long evolutionary history. A likely function of RNAi throughout that history is to protect the genome from both pathogenic and parasitic invaders.
authors.affiliation: Watson School of Biological Sciences, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Aravin
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Hannon
authors.forename: Julius
authors.initials: J
authors.lastname: Brennecke
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D060565:Argonaute Proteins; D001483:Base Sequence; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D019143:Evolution, Molecular; D020868:Gene Silencing; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D034743:RNA-Induced Silencing Complex
chemical_list: D060565:Argonaute Proteins; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D011506:Proteins; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D034743:RNA-Induced Silencing Complex; C116498:piwi protein, Drosophila