title: RNA-interference components are dispensable for transcriptional silencing of the drosophila bithorax-complex.
abstract: BACKGROUND
  Beyond their role in post-transcriptional gene silencing, Dicer and Argonaute, two components of the RNA interference (RNAi) machinery, were shown to be involved in epigenetic regulation of centromeric heterochromatin and transcriptional gene silencing. In particular, RNAi mechanisms appear to play a role in repeat induced silencing and some aspects of Polycomb-mediated gene silencing. However, the functional interplay of RNAi mechanisms and Polycomb group (PcG) pathways at endogenous loci remains to be elucidated.
  
  
  RESULTS
  Here we show that the endogenous Dicer-2/Argonaute-2 RNAi pathway is dispensable for the PcG mediated silencing of the homeotic Bithorax Complex (BX-C). Although Dicer-2 depletion triggers mild transcriptional activation at Polycomb Response Elements (PREs), this does not induce transcriptional changes at PcG-repressed genes. Moreover, Dicer-2 is not needed to maintain global levels of methylation of lysine 27 of histone H3 and does not affect PRE-mediated higher order chromatin structures within the BX-C. Finally bioinformatic analysis, comparing published data sets of PcG targets with Argonaute-2-bound small RNAs reveals no enrichment of these small RNAs at promoter regions associated with PcG proteins.
  
  
  CONCLUSIONS
  We conclude that the Dicer-2/Argonaute-2 RNAi pathway, despite its role in pairing sensitive gene silencing of transgenes, does not have a role in PcG dependent silencing of major homeotic gene cluster loci in Drosophila.
authors.affiliation: Epigenetics and Genome Reprogramming Laboratory, IRCCS Fondazione Santa Lucia, Rome, Italy. filippo.cernilogar@med.uni-muenchen.de
authors.forename: Filippo M
authors.initials: FM
authors.lastname: Cernilogar
authors.forename: A Maxwell
authors.initials: AM
authors.lastname: Burroughs
authors.forename: Chiara
authors.initials: C
authors.lastname: Lanzuolo
authors.forename: Achim
authors.initials: A
authors.lastname: Breiling
authors.forename: Axel
authors.initials: A
authors.lastname: Imhof
authors.forename: Valerio
authors.initials: V
authors.lastname: Orlando
mesh_terms: D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D020868:Gene Silencing; D006657:Histones / Q000378:metabolism; D008745:Methylation; D063146:Polycomb-Group Proteins / Q000378:metabolism; D020365:RNA Helicases / Q000378:metabolism; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D043244:Ribonuclease III / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C433807:AGO2 protein, Drosophila; D060565:Argonaute Proteins; D029721:Drosophila Proteins; D006657:Histones; D063146:Polycomb-Group Proteins; D012330:RNA, Double-Stranded; C478069:DCR-2 protein, Drosophila; D043244:Ribonuclease III; D020365:RNA Helicases