title: Transcriptional silencing of a transgene by RNAi in the soma of C. elegans.
abstract: The silencing of transgene expression at the level of transcription in the soma of Caenorhabditis elegans through an RNAi-dependent pathway has not been previously characterized. Most gene silencing due to RNAi in C. elegans occurs at the post-transcriptional level. We observed transcriptional silencing when worms containing the elt-2::gfp/LacZ transgene were fed RNA produced from the commonly used L4440 vector. The transgene and the vector share plasmid backbone sequences. This transgene silencing depends on multiple RNAi pathway genes, including dcr-1, rde-1, rde-4, and rrf-1. Unlike post-transcriptional gene silencing in worms, elt-2::gfp/LacZ silencing is dependent on the PAZ-PIWI protein Alg-1 and on the HP1 homolog Hpl-2. The latter is a chromatin silencing factor, and expression of the transgene is inhibited at the level of intron-containing precursor mRNA. This inhibition is accompanied by a decrease in the acetylation of histones associated with the transgene. This transcriptional silencing in the soma can be distinguished from transgene silencing in the germline by its inability to be transmitted across generations and its dependence on the rde-1 gene. We therefore define this type of silencing as RNAi-induced Transcriptional Gene Silencing (RNAi-TGS). Additional chromatin-modifying components affecting RNAi-TGS were identified in a candidate RNAi screen.
authors.affiliation: Center for Cancer Research, McGovern Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Alla
authors.initials: A
authors.lastname: Grishok
authors.forename: Jina L
authors.initials: JL
authors.lastname: Sinskey
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Sharp
mesh_terms: D000107:Acetylation; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics; D003001:Cloning, Molecular; D017931:DNA Primers; D004722:Endoribonucleases / Q000235:genetics; D050980:GATA Transcription Factors; D020868:Gene Silencing; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins; D006657:Histones / Q000378:metabolism; D047468:Immunoprecipitation; D007763:Lac Operon / Q000235:genetics; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043244:Ribonuclease III; D014157:Transcription Factors / Q000235:genetics; D019076:Transgenes / Q000235:genetics*
chemical_list: D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; C094134:ELT-2 protein, C elegans; D050980:GATA Transcription Factors; D006657:Histones; C461645:RDE-4 protein, C elegans; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D014157:Transcription Factors; C122185:rde-1 protein, C elegans; D049452:Green Fluorescent Proteins; D004722:Endoribonucleases; C118116:dcr-1 protein, C elegans; D043244:Ribonuclease III
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