title: Plant-specific multisubunit RNA polymerase in gene silencing.
abstract: In recent years, a major breakthrough in the study of epigenetic silencing in eukaryotes came with the discovery that the RNA-interference pathway (RNAi) is generally implicated in heterochromatin assembly and gene silencing. An important and paradoxical feature of the RNAi-mediated heterochromatin pathways is their requirement for some form of transcription. In fission yeast, Schizosaccharomyces pombe, centromeric siRNAs have been shown to derive from chromatin-bound nascent transcripts produced by RNA polymerase II (PolII) at the site of heterochromatin formation. Likewise, chromatin-bound nascent transcripts generated by a PolII-related DNA-dependent RNA polymerase, known as PolIVb/PolV, have recently been implicated in RNA-directed DNA methylation (RdDM), the prominent RNAi-mediated chromatin pathway in plants. In this review we discuss recent work on the plant-specific PolII variant enzymes and discuss the mechanistic convergences that have been observed in the role of these enzymes in their respective siRNA-mediated heterochromatin formation pathways.
authors.affiliation: Laboratoire Génome et Développement des Plantes (LGDP), CNRS/IRD/Université de Perpignan UMR 5096, Perpignan, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lahmy
authors.forename: Natacha
authors.initials: N
authors.lastname: Bies-Etheve
authors.forename: Thierry
authors.initials: T
authors.lastname: Lagrange
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D002503:Centromere / Q000648:ultrastructure; D002843:Chromatin / Q000378:metabolism; D019175:DNA Methylation; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000235:genetics*; D020868:Gene Silencing; D006570:Heterochromatin / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D010944:Plants / Q000201:enzymology* / Q000235:genetics*; D034622:RNA Interference; D012319:RNA Polymerase II / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D006570:Heterochromatin; D034741:RNA, Small Interfering; D029702:Schizosaccharomyces pombe Proteins; D012319:RNA Polymerase II; D012321:DNA-Directed RNA Polymerases