title: Revisiting RNA-directed DNA methylation.
abstract: RNA-directed DNA methylation (RdDM) involves sequence-specific guiding of the de novo methylation machinery to complementary genomic DNA by RNA molecules. It is still elusive whether guide RNAs bind directly to DNA or to nascent transcripts produced from it. Even the nature of the guide RNAs is not elucidated. RNA interference (RNAi) studies provided a link between RNAi and RdDM indicating that small interfering RNAs (siRNAs) trigger and guide cytosine methylation. The "siRNA hypothesis" is generally accepted. However, recent data demonstrated that RdDM is not always associated with the accumulation of corresponding siRNAs. RdDM triggers may differ from guide RNAs and further studies are needed to clarify if guide RNAs are small or long RNAs, if they are single or double stranded and if they target DNA or nascent transcript.
authors: RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany.
authors: Athanasios
authors: A
authors: Dalakouras
authors: Michael
authors: M
authors: Wassenegger
mesh_terms: D003596:Cytosine / Q000378:metabolism*; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D018745:Genome, Plant; D008958:Models, Molecular; D010944:Plants / Q000235:genetics* / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism*; D058727:RNA, Small Untranslated / Q000378:metabolism*
chemical_list: D018749:RNA, Plant; D034741:RNA, Small Interfering; D058727:RNA, Small Untranslated; D003596:Cytosine
keywords: DNA methylation; DNA-DEPENDENT RNA POLYMERASEs; RNA interference; double stranded RNA; methylC-seq; plants; small RNAs