Project description:microRNAs (miRNAs) are typically generated as ~22-nucleotide double-stranded RNAs via processing of precursor hairpins by the RNase III enzyme Dicer, after which they are loaded into Argonaute (Ago) proteins to form RNA-induced silencing complex (RISC). However, the biogenesis of miR-451, an erythropoietic miRNA conserved in vertebrates, does not require Dicer processing. Instead, the short pre-miR-451 precursor hairpin is directly loaded into Ago, followed by cleavage of the 3' arm and trimming of the 3' end to the mature length by PARN. Here we show the in vivo activity of miR-430 Ago2-hairpin, a canonical microRNA engineered to fit the structure of miR-451 and hence become Ago2-dependent. Moreover, we test a modified miR-430 Ago2-haipin with 3x phoshorothioate bonds that impairs trimmng. Surprisingly, our data show that trimming of Ago-cleaved pre-miRNAs is not essential for target silencing, indicating that RISC is functional with miRNAs longer than 22-nucleotides. Rescue of MZdicer zebrafish mutant with the injection of trimmable and nontrimmable miR-430 Ago2 hairpins: Transcriptome of wild type, MZdicer mutant, and MZdicer mutant micoinjected with miR-430 duplex, miR-430 (Ago2-haripin), miR-430 (Ago2-haripin 3xPhosphorothioate)
Project description:microRNAs (miRNAs) are typically generated as ~22-nucleotide double-stranded RNAs via processing of precursor hairpins by the RNase III enzyme Dicer, after which they are loaded into Argonaute (Ago) proteins to form RNA-induced silencing complex (RISC). However, the biogenesis of miR-451, an erythropoietic miRNA conserved in vertebrates, does not require Dicer processing. Instead, the short pre-miR-451 precursor hairpin is directly loaded into Ago, followed by cleavage of the 3' arm and trimming of the 3' end to the mature length by PARN. Here we show the in vivo activity of miR-430 Ago2-hairpin, a canonical microRNA engineered to fit the structure of miR-451 and hence become Ago2-dependent. Moreover, we test a modified miR-430 Ago2-haipin with 3x phoshorothioate bonds that impairs trimmng. Surprisingly, our data show that trimming of Ago-cleaved pre-miRNAs is not essential for target silencing, indicating that RISC is functional with miRNAs longer than 22-nucleotides.
Project description:We show that target mRNAs trigger the non-templated addition of nucleotides (mainly adenosines and uridines) and shortening of their cognate miRNAs in primary hippocampal neurons. The induced effect is observable both in total RNA and in Ago2-associated RNA, demonstrating that the process is initiated in Ago2 bound miRNAs. Illumina Small RNA sequencing was performed on rat hippocampal neurons infected with different target mRNAs in different conditions. The data includes 3 independent experiments: 1. Hippocampal neurons (DIV15) 6 days after transducing them with target mRNAs (driven by the Synapsin promoter) against different miRNAs. Samples are titled "Syn-Target". Samples transduced with targets containing extensive complementarity are labeled "Ext" and those with Seed complementarity are labeled "Seed". 2. Hippocampal neurons (DIV16) 7 days after transducing them with an inducible target mRNA against miR-132, and inducing for different times with Doxycycline. Samples are titled "Time-course" 3. Hippocampal neurons (DIV16) 7 days after co-transducing them with FLAG/HA-Ago2 plus an inducible target mRNA against miR-132, and inducing them for different times with Doxycycline. Samples are titled "Time-course_Ago2"
Project description:We established a neuron-specific Argonaute2:GFP-RNA immunoprecipitation followed by high throughput sequencing (AGO2-RIP-seq) to analyse the regulatory role of miRNAs in mouse hippocampal neurons. Using this technique, we identified more than two thousand miRNA target genes in hippocampal neurons, regulating essential neuronal features such as axon guidance and transcription. Furthermore, we found that stable inhibition of the highly expressed miR-124 in hippocampal neurons led to significant changes in the AGO2 binding of target mRNAs, resulting in subsequent upregulation of numerous miRNA target genes. Our data suggest that target redundancies are common among microRNA families. Together, these findings greatly enhance our understanding of the mechanisms and dynamics through which miRNAs regulate their target genes in neurons. Analysis of the miRNA targetome in hippocampal neurons after inhibition of 2 different miRNAs. AAV5 injections into the hippocampus of adult C57BL/6 mice producing either of the following under a synapsin promoter: GFP only (Samples beginning with 'GFP124…' or 'GFP125…'), GFP-miR124sp (Samples beginning with 'miR124…'), GFP-miR125sp (Samples beginning with 'miR125…'), GFP-AGO2-miR292sponge (samples ending with '…292'), GFP-AGO2-miR124sponge (samples ending with '…124'), GFP-AGO2-miR125sponge (samples ending with '…125'). All other samples were sham-injected.
Project description:Rates of production and degradation together specify microRNA (miRNA) abundance and dynamics. Here, we used approach-to-steady-state metabolic labeling to assess these rates for 176 miRNAs in contact-inhibited mouse embryonic fibroblasts (MEFs), 182 miRNAs in dividing MEFs, and 127 miRNAs in mouse embryonic stem cells (mESCs). MicroRNA duplexes, each comprising a mature miRNA and its passenger strand, are produced at rates as fast as 110 ± 50 copies/cell per min, which exceeds rates reported for any mRNAs. These duplexes are rapidly loaded into Argonaute, with < 10 min typically required for duplex loading and silencing-complex maturation. Within Argonaute, guide strands have stabilities that vary by 100-fold. Half-lives also vary globally between cell lines, with median values ranging from 11 to 34 h in mESCs and contact-inhibited MEFs, respectively. Moreover, relative half-lives for individual miRNAs vary between cell types, implying the influence of cell-specific factors in dictating turnover rate. The apparent influence of miRNA regions most important for targeting, together with the effect of one target on miR-7 accumulation, suggest that targets fulfill this role. Analysis of the tailing and trimming of miRNA 3 termini showed that the flux was typically greatest through the isoform tailed with a single uridine, although changes in this flux did not correspond to changes in stability, which suggested that the processes of tailing and trimming might be independent from that of decay. Together these results establish a framework for describing the dynamics and regulation of miRNAs throughout their lifecycle.
Project description:We show that target mRNAs trigger the non-templated addition of nucleotides (mainly adenosines and uridines) and shortening of their cognate miRNAs in primary hippocampal neurons. The induced effect is observable both in total RNA and in Ago2-associated RNA, demonstrating that the process is initiated in Ago2 bound miRNAs.
Project description:MicroRNAs (miRNAs) act in concert with Argonaute (AGO) proteins to broadly repress mRNA targets. After AGO loading, miRNAs generally exhibit slow turnover. An important exception occurs when miRNAs encounter targets with extensive complementarity, which can trigger a process termed target-directed microRNA degradation (TDMD). Prevailing models of TDMD invoke miRNA tailing and trimming as an essential step in the decay mechanism. Here, a genome-wide screen revealed a novel cullin-RING ubiquitin ligase, which we named the DECAY complex, that mediates TDMD. The DECAY complex interacts with AGO proteins, mediates TDMD induced by multiple transcripts, and does not require tailing and trimming to elicit miRNA turnover. Based upon these findings, we propose a model in which the DECAY complex mediates TDMD by promoting proteasomal decay of miRNA-containing complexes.
Project description:MicroRNAs (miRNAs) act in concert with Argonaute (AGO) proteins to broadly repress mRNA targets. After AGO loading, miRNAs generally exhibit slow turnover. An important exception occurs when miRNAs encounter targets with extensive complementarity, which can trigger a process termed target-directed microRNA degradation (TDMD). Prevailing models of TDMD invoke miRNA tailing and trimming as an essential step in the decay mechanism. Here, a genome-wide screen revealed a novel cullin-RING ubiquitin ligase, which we named the DECAY complex, that mediates TDMD. The DECAY complex interacts with AGO proteins, mediates TDMD induced by multiple transcripts, and does not require tailing and trimming to elicit miRNA turnover. Based upon these findings, we propose a model in which the DECAY complex mediates TDMD by promoting proteasomal decay of miRNA-containing complexes.
Project description:MicroRNAs (miRNAs) act in concert with Argonaute (AGO) proteins to broadly repress mRNA targets. After AGO loading, miRNAs generally exhibit slow turnover. An important exception occurs when miRNAs encounter targets with extensive complementarity, which can trigger a process termed target-directed microRNA degradation (TDMD). Prevailing models of TDMD invoke miRNA tailing and trimming as an essential step in the decay mechanism. Here, a genome-wide screen revealed a novel cullin-RING ubiquitin ligase, which we named the DECAY complex, that mediates TDMD. The DECAY complex interacts with AGO proteins, mediates TDMD induced by multiple transcripts, and does not require tailing and trimming to elicit miRNA turnover. Based upon these findings, we propose a model in which the DECAY complex mediates TDMD by promoting proteasomal decay of miRNA-containing complexes.
Project description:We established a neuron-specific Argonaute2:GFP-RNA immunoprecipitation followed by high throughput sequencing (AGO2-RIP-seq) to analyse the regulatory role of miRNAs in mouse hippocampal neurons. Using this technique, we identified more than two thousand miRNA target genes in hippocampal neurons, regulating essential neuronal features such as axon guidance and transcription. Furthermore, we found that stable inhibition of the highly expressed miR-124 in hippocampal neurons led to significant changes in the AGO2 binding of target mRNAs, resulting in subsequent upregulation of numerous miRNA target genes. Our data suggest that target redundancies are common among microRNA families. Together, these findings greatly enhance our understanding of the mechanisms and dynamics through which miRNAs regulate their target genes in neurons.