title: Posttranscriptional gene silencing in nuclei.
abstract: In plants, small interfering RNAs (siRNAs) with sequence homology to transcribed regions of genes can guide the sequence-specific degradation of corresponding mRNAs, leading to posttranscriptional gene silencing (PTGS). The current consensus is that siRNA-mediated PTGS occurs primarily in the cytoplasm where target mRNAs are localized and translated into proteins. However, expression of an inverted-repeat double-stranded RNA corresponding to the soybean FAD2-1A desaturase intron is sufficient to silence FAD2-1, implicating nuclear precursor mRNA (pre-mRNA) rather than cytosolic mRNA as the target of PTGS. Silencing FAD2-1 using intronic or 3'-UTR sequences does not affect transcription rates of the target genes but results in the strong reduction of target transcript levels in the nucleus. Moreover, siRNAs corresponding to pre-mRNA-specific sequences accumulate in the nucleus. In Arabidopsis, we find that two enzymes involved in PTGS, Dicer-like 4 and RNA-dependent RNA polymerase 6, are localized in the nucleus. Collectively, these results demonstrate that siRNA-directed RNA degradation can take place in the nucleus, suggesting the need for a more complex view of the subcellular compartmentation of PTGS in plants.
authors.affiliation: Monsanto, Calgene Campus, Davis, CA 95616, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Hoffer
authors.forename: Sergey
authors.initials: S
authors.lastname: Ivashuta
authors.forename: Olga
authors.initials: O
authors.lastname: Pontes
authors.forename: Alexa
authors.initials: A
authors.lastname: Vitins
authors.forename: Craig
authors.initials: C
authors.lastname: Pikaard
authors.forename: Andrew
authors.initials: A
authors.lastname: Mroczka
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wagner
authors.forename: Toni
authors.initials: T
authors.lastname: Voelker
mesh_terms: D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D007438:Introns / Q000235:genetics; D008856:Microscopy, Fluorescence; D034622:RNA Interference / Q000502:physiology*; D012322:RNA Precursors / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043244:Ribonuclease III / Q000378:metabolism; D013025:Glycine max
chemical_list: D029681:Arabidopsis Proteins; D012322:RNA Precursors; D034741:RNA, Small Interfering; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase; C514575:RDR6 protein, Arabidopsis; D012324:RNA-Dependent RNA Polymerase; C504982:DCL4 protein, Arabidopsis; D043244:Ribonuclease III