title: RNAa in action: from the exception to the norm.
abstract: Small RNA programmed Argonautes are sophisticated cellular effector platforms known to be involved in a diverse array of functions ranging from mRNA cleavage, translational inhibition, DNA elimination, epigenetic silencing, alternative splicing and even gene activation. First observed in human cells, small RNA-induced gene activation, also known as RNAa, involves the targeted recruitment of Argonaute proteins to specific promoter sequences followed by induction of stable epigenetic changes which promote transcription. The existence of RNAa remains contentious due to its elusive mechanism. A string of recent studies in C. elegans provides unequivocal evidence for RNAa's fundamental role in sculpting the epigenetic landscape and maintaining active transcription of endogenous genes and supports the presence of a functionally sophisticated network of small RNA-Argonaute pathways consisting of opposite yet complementary "yin and yang" regulatory elements. In this review, we summarize key findings from recent studies of endogenous RNAa in C. elegans, with an emphasis on the Argonaute protein CSR-1.
authors.affiliation: a Laboratory of Molecular Medicine; Peking Union Medical College Hospital; Chinese Academy of Medical Sciences and Peking Union Medical College ; Beijing , China.
authors.forename: Dan
authors.initials: D
authors.lastname: Guo
authors.forename: Liam
authors.initials: L
authors.lastname: Barry
authors.forename: Sharon Szu Hua
authors.initials: SS
authors.lastname: Lin
authors.forename: Vera
authors.initials: V
authors.lastname: Huang
authors.forename: Long-Cheng
authors.initials: LC
authors.lastname: Li
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D018510:RNA, Helminth / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics*
chemical_list: C544459:CSR-1 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; D018510:RNA, Helminth; D012333:RNA, Messenger; D034741:RNA, Small Interfering
keywords: Argonaute; LCE, lin-4 complementary element; RDRP, RNA-dependent RNA polymerase; RISC, RNA induced silencing complex; RNAa; RNAa, RNA activation; RNAe; RNAe, RNA-induced epigenetic silencing; RNAi, RNA interference; TSS, transcription start site; WAGO, worm-specific AGO; epigenetic memory; gene expression; miRNAa, miRNA induced RNAa; piRNA, Piwi-interacting RNA