Project description:blan08_rnapaths; Analyses of endogenous rna substrates of xrn and exosome and ptgs pathways What are the endogenous RNA substrates co-regulated by RQC and PTGS pathways? Genome-wide analyses of endogenous RNA substrates of RNA Quality Control pathways; wild type versus 15 mutants.
Project description:blan08_rnapaths; Analyses of endogenous rna substrates of xrn and exosome and ptgs pathways What are the endogenous RNA substrates co-regulated by RQC and PTGS pathways? Genome-wide analyses of endogenous RNA substrates of RNA Quality Control pathways; wild type versus 15 mutants. 30 dye-swap - gene knock in (transgenic), gene knock out
Project description:RNA quality control (RQC) and post-transcriptional gene silencing (PTGS) target and degrade aberrant endogenous RNAs and foreign RNAs, contributing to homeostasis of cellular RNAs. In plants, RQC and PTGS compete for foreign and selected endogenous RNAs; however, little is known about the mechanism interconnecting the two pathways. Using a reporter system designed for monitoring PTGS, we revealed that the 26S proteasome subunit RPT2a enhances transgene PTGS by promoting the accumulation of transgene-derived short interfering RNAs without affecting their biogenesis. RPT2a physically associated with a subset of RQC components and downregulated the protein level. Overexpression of the RQC components interfered with transgene silencing, and impairment of the RQC machinery reinforced transgene PTGS attenuated by rpt2a. Overall, we demonstrate that the 26S proteasome subunit RPT2a promotes PTGS by repressing the RQC machinery to control foreign RNAs.
Project description:Transgene loci that spontaneously undergo RNA silencing have been instrumental to decipher RNA silencing pathways in plants. In contrast, transgene loci that are stably expressed have been poorly characterized. Here we show that stably expressed transgene loci epigenetically differ from endogenous genes. Impairing the histone H3K4me3 demethylase JMJ14 increases DNA methylation at stably expressed transgene loci but not at endogenous genes, whereas impairing the histone H3K9me2 demethylase IBM1 increases DNA methylation at endogenous genes, but decreases DNA methylation at stably expressed transgene loci. Moreover, impairing IBM1 promotes post-transcriptional gene silencing (PTGS) at stably expressed transgene loci, whereas impairing JMJ14 prevents PTGS induced systemically by grafting onto silenced rootstocks. Given that impairing DNA methylation suppresses the effect of impairing JMJ14 and restores transgene capacity to undergo graft-induced PTGS, we propose that transgene DNA methylation prevents PTGS, likely by limiting the transcription of aberrant RNA by-products that are transformed into dsRNA by cellular RNA-dependent RNA polymerases to activate PTGS.
Project description:The RNA exosome is a key 3’-5’ exoribonuclease with evolutionary conserved structure and roles. Its cytosolic functions require the co-factors SKI7 and the Ski complex. Here we demonstrate by co-purification experiments that the ARM repeat protein RESURRECTION1 (RST1) and RST1 INTERACTING PROTEIN (RIPR) connect the cytosolic Arabidopsis RNA exosome to the Ski complex. rst1 and ripr mutants accumulate small RNAs many of which are quality control siRNAs (rqc-siRNAs) produced by the postranscriptional gene silencing (PTGS) machinery when mRNA degradation is compromised. Indeed, quasi identical small RNA populations are observed in mutants lacking the RRP45B/CER7 subunit of the core exosome. This biochemical and genetic evidence supports a physical and functional link between RST1, RIPR and the RNA exosome. Our data reveal the existence of additional cytosolic exosome co-factors besides the known SKI subunits. Interestingly, RST1 is not restricted to plants, as homologues with a similar domain architecture exist in animals, including humans.
Project description:Background: Cytoplasmic degradation of endogenous RNAs is an integral part of RNA quality control (RQC) and often relies on the removal of the 5' cap structure and their subsequent 5’ to 3’ degradation. In parallel, many eukaryotes degrade exogenous and selected endogenous RNAs through post-transcriptional gene silencing (PTGS). In plants, PTGS depends on small interfering (si)RNAs produced after the conversion of single-stranded RNAs to double-stranded RNAs by the cellular RNA DEPENDENT RNA POLYMERASE 6 (RDR6). PTGS and RQC compete for transgene-derived RNAs, but it is unknown whether this competition also occurs for endogenous transcripts. Results: We show that that upon decapping impairment hundreds of endogenous mRNAs give rise to a new class of siRNAs, a subset of which depends on RDR6 for their production. Conclusions: Our results suggest that the decapping of aberrant endogenous RNA in P-bodies limits their entry into the PTGS pathway and prevents the subsequent deleterious consequences arising from this entry. We anticipate that the siRNAs identified in decapping mutants represent a subset of a larger ensemble of endogenous siRNAs that we coin rqc-siRNAs because they accumulate when RQC processes are impaired.
Project description:Background: Cytoplasmic degradation of endogenous RNAs is an integral part of RNA quality control (RQC) and often relies on the removal of the 5' cap structure and their subsequent 5M-bM-^@M-^Y to 3M-bM-^@M-^Y degradation. In parallel, many eukaryotes degrade exogenous and selected endogenous RNAs through post-transcriptional gene silencing (PTGS). In plants, PTGS depends on small interfering (si)RNAs produced after the conversion of single-stranded RNAs to double-stranded RNAs by the cellular RNA DEPENDENT RNA POLYMERASE 6 (RDR6). PTGS and RQC compete for transgene-derived RNAs, but it is unknown whether this competition also occurs for endogenous transcripts. Results: We show that that upon decapping impairment hundreds of endogenous mRNAs give rise to a new class of siRNAs, a subset of which depends on RDR6 for their production. Conclusions: Our results suggest that the decapping of aberrant endogenous RNA in P-bodies limits their entry into the PTGS pathway and prevents the subsequent deleterious consequences arising from this entry. We anticipate that the siRNAs identified in decapping mutants represent a subset of a larger ensemble of endogenous siRNAs that we coin rqc-siRNAs because they accumulate when RQC processes are impaired. Small RNA-seq experiments performed in duplicates for each condition.
Project description:Next-generation Illumina sequencing technology was used to analyze small RNA associated with post-transcriptional gene silencing induced by intron-spliced hairpin RNA (ihpRNA) in Arabidopsis. The experimental induction of RNA silencing in plants often involves expression of transgenes encoding inverted repeat (IR) sequences to produce abundant dsRNAs that are processed into small RNAs (sRNAs). These sRNAs are key mediators of post-transcriptional gene silencing (PTGS) and determine the specificity of the inhibition of gene expression. Despite its broad utility as a research tool, IR-PTGS is only a partially understood mechanism of RNA silencing in plants. We generated four sets of 60 Arabidopsis plants, each containing IR transgenes expressing different configurations of uidA and CHALCONE SYNTHASE (CHS) gene fragments. The levels of PTGS were dependent on the orientation and position of the fragment in the IR construct. To investigate these differences, we characterized the sRNA profiles by Illumina sequencing of seven libraries generated from transgenic families showing different levels of IR-PTGS. Mapping of sRNA sequences to their corresponding transgene-derived and endogenous transcripts identified distinctive patterns of differential sRNA accumulation. Analyses of these patterns and peaks revealed similarities among sRNAs associated with IR-PTGS and endogenous sRNAs linked to uncapped mRNA decay. We also found unexpected associations between sRNA accumulation and the presence of predicted open reading frames in the trigger sequence. Our observations provide new guidelines for designing constructs to increase the efficiency of IR-PTGS. In addition, strong IR-PTGS affected the prevalence of endogenous sRNAs, which has implications for the use of PTGS for experimental or applied purposes.
Project description:Next-generation Illumina sequencing technology was used to analyze small RNA associated with post-transcriptional gene silencing induced by intron-spliced hairpin RNA (ihpRNA) in Arabidopsis. The experimental induction of RNA silencing in plants often involves expression of transgenes encoding inverted repeat (IR) sequences to produce abundant dsRNAs that are processed into small RNAs (sRNAs). These sRNAs are key mediators of post-transcriptional gene silencing (PTGS) and determine the specificity of the inhibition of gene expression. Despite its broad utility as a research tool, IR-PTGS is only a partially understood mechanism of RNA silencing in plants. We generated four sets of 60 Arabidopsis plants, each containing IR transgenes expressing different configurations of uidA and CHALCONE SYNTHASE (CHS) gene fragments. The levels of PTGS were dependent on the orientation and position of the fragment in the IR construct. To investigate these differences, we characterized the sRNA profiles by Illumina sequencing of seven libraries generated from transgenic families showing different levels of IR-PTGS. Mapping of sRNA sequences to their corresponding transgene-derived and endogenous transcripts identified distinctive patterns of differential sRNA accumulation. Analyses of these patterns and peaks revealed similarities among sRNAs associated with IR-PTGS and endogenous sRNAs linked to uncapped mRNA decay. We also found unexpected associations between sRNA accumulation and the presence of predicted open reading frames in the trigger sequence. Our observations provide new guidelines for designing constructs to increase the efficiency of IR-PTGS. In addition, strong IR-PTGS affected the prevalence of endogenous sRNAs, which has implications for the use of PTGS for experimental or applied purposes. Sequencing of small RNA from Arabidopsis plants transformed with ihpRNA constructs. Seven small RNA libraries were sequenced: Lib 0, made from non-transgenic Arabidopsis plants, and Libs 1-6, made from plants transformed with different configurations of ihpRNA.
Project description:The LSM2-8 complex specifically targets nuclear RNAs generated from loci bearing histone H3K27me3 for degradation through the exonuclease XRN-2 In fission yeast and plants RNA-processing pathways including co-transcriptional degradation of nuclear mRNAs contributes to heterochromatic gene silencing additionally to the well-known transcriptional repression, but it was not knownunclear if this extra level of regulation also to occur in metazoans. Here we report the discovery of a related pathway in somatic cells of the flatworm C. elegans. The highly conserved, RNA binding LSM2-8 complex is shown to silence selectively heterochromatic reporters and endogenous genes bearing the Polycomb mark H2K27me3. LSM2-8-mediated silencing is independent of H3K9me2/me3 but depends on mes-2, the Polycomb-like histone methyl transferase. LSM2-8-mediated silencing is detectable from early embryonic stages through adulthood. The LSM2-8 complex works cooperatively with XRN-2, a 5’-3’ exonuclease, and disruption of the pathway leads to stabilized targeted mRNAs. Developmental defects and premature death were observed in worms lacking LSM-8, and levels of H3K27me3 dropped slightly at Pc-targeted loci. LSM2-8-mediated silencing of H3K27me3-bound regions defines a new mechanism of selective heterochromatin gene silencing not previously shown for higher eukaryotes.