Project description:Nonsense-mediated decay (NMD) is a translation-dependent RNA quality control mechanism that occurs in the cytoplasm. However, it is unknown how NMD regulates the stability of RNAs translated at the Endoplasmic Reticulum (ER). Here, we identify a localized NMD pathway dedicated to ER-translated mRNAs. We previously identified NBAS, a component of the Syntaxin 18 complex involved in Golgi-to-ER trafficking, as a novel NMD factor. Here, we show that NBAS fulfils an independent function in NMD. This ER-NMD pathway requires the interaction of NBAS with the core NMD factor UPF1, which is partially localized at the ER in the proximity of the translocon. NBAS and UPF1 co-regulate the stability of ER-associated transcripts, in particular those associated with the cellular stress response. We propose a model where NBAS recruits UPF1 to the membrane of the ER and activates an ER-dedicated NMD pathway, thus providing an ER protective function by ensuring quality control of ER-translated mRNAs.
Project description:Nonsense-mediated decay (NMD) is a translation-dependent RNA quality control mechanism that occurs in the cytoplasm. However, it is unknown how NMD regulates the stability of RNAs translated at the Endoplasmic Reticulum (ER). Here, we identify a localized NMD pathway dedicated to ER-translated mRNAs. We previously identified NBAS, a component of the Syntaxin 18 complex involved in Golgi-to-ER trafficking, as a novel NMD factor. Here, we show that NBAS fulfils an independent function in NMD. This ER-NMD pathway requires the interaction of NBAS with the core NMD factor UPF1, which is partially localized at the ER in the proximity of the translocon. NBAS and UPF1 co-regulate the stability of ER-associated transcripts, in particular those associated with the cellular stress response. We propose a model where NBAS recruits UPF1 to the membrane of the ER and activates an ER-dedicated NMD pathway, thus providing an ER protective function by ensuring quality control of ER-translated mRNAs.
Project description:Nonsense-mediated mRNA decay (NMD) is a conserved RNA surveillance pathway that is an important modulator of disease pathology and is required for embryonic development. Despite significant research effort, the rules that govern NMD remain incompletely understood. Here we used a combined¬ approach, integrating RNA-Seq, ribosome footprinting, and CLIP-Seq analysis of the essential NMD factor Upf1, to provide a more complete picture of the role of NMD in modulating gene expression in murine embryonic stem cells (mESCs). We show that presence of an exon-exon junction ?50 nucleotides (nt) downstream of a termination codon (dEJ) contributes to NMD independently of 3' UTR length, but has stronger effects in genes with shorter 3' UTRs. We also map translated upstream open reading frames (uORFs) in mESCs and show that they are associated with NMD regulation, especially of genes encoding transcription factors, and we find that lowly translated mRNAs can escape NMD. Finally, we identify over 200 direct binding targets of Upf1 and describe a pathway of Upf1-dependent gene regulation reliant on Upf1 binding to the 3' UTR and independent of presence of a dEJ. Together, these analyses characterize known and discover novel determinants of NMD and establish a broader role in mESC gene regulation for Upf1. mRNA-Seq analysis of wildtype (2 samples), translationally inhibited (by cycloheximide treatment, 2 samples), control-depleted (2 samples), and Upf1-depleted (4 samples) mouse embryonic stem cells (mESCs); CLIP-Seq analysis of Upf1 (5 samples, and 5 samples of IgG control CLIP-Seq); Ribosome footprint profiling of wildtype (1 sample), control-depleted (1 sample), and Upf1-depleted (1 sample) mESCs
Project description:High-throughput sequencing of RNA isolated by crosslinking immunoprecipitation (HITS-CLIP) allows for high resolution, genome-wide mapping of RNA-binding proteins. We found that substantial mispriming during reverse transcription results in the overrepresentation of sequences complementary to the primer used for reverse transcription. Up to 45% of peaks in publicly available HITS-CLIP libraries are attributable to this artifact, and the majority of libraries have detectable levels of mispriming. We also found that standard techniques for validating miRNA-target interactions fail to differentiate between artifactual peaks and physiologically relevant peaks. Here, we present a modification to the HITS-CLIP protocol that effectively eliminates this artifact. Argonaute HITS-CLIP on the MCF-7 breast cancer cell line treated with 17β-estradiol for 0, 6 or 24 hours using a nested reverse transcriptions pimer and protected or unprotected reverse PCR primers for library amplification.
Project description:High-throughput sequencing of RNA isolated by crosslinking immunoprecipitation (HITS-CLIP) allows for high resolution, genome-wide mapping of RNA-binding proteins. We found that substantial mispriming during reverse transcription results in the overrepresentation of sequences complementary to the primer used for reverse transcription. Up to 45% of peaks in publicly available HITS-CLIP libraries are attributable to this artifact, and the majority of libraries have detectable levels of mispriming. We also found that standard techniques for validating miRNA-target interactions fail to differentiate between artifactual peaks and physiologically relevant peaks. Here, we present a modification to the HITS-CLIP protocol that effectively eliminates this artifact.
Project description:Nonsense-mediated mRNA decay (NMD) is a conserved RNA surveillance pathway that is an important modulator of disease pathology and is required for embryonic development. Despite significant research effort, the rules that govern NMD remain incompletely understood. Here we used a combined¬ approach, integrating RNA-Seq, ribosome footprinting, and CLIP-Seq analysis of the essential NMD factor Upf1, to provide a more complete picture of the role of NMD in modulating gene expression in murine embryonic stem cells (mESCs). We show that presence of an exon-exon junction ≥50 nucleotides (nt) downstream of a termination codon (dEJ) contributes to NMD independently of 3' UTR length, but has stronger effects in genes with shorter 3' UTRs. We also map translated upstream open reading frames (uORFs) in mESCs and show that they are associated with NMD regulation, especially of genes encoding transcription factors, and we find that lowly translated mRNAs can escape NMD. Finally, we identify over 200 direct binding targets of Upf1 and describe a pathway of Upf1-dependent gene regulation reliant on Upf1 binding to the 3' UTR and independent of presence of a dEJ. Together, these analyses characterize known and discover novel determinants of NMD and establish a broader role in mESC gene regulation for Upf1.
Project description:To assess the requirement of Nova2 for alternative processing of RNA in mouse brain. Protein-RNA interactions play critical roles in all aspects of gene expression. Here we develop a genome-wide means of mapping protein-RNA binding sites in vivo, by high throughput sequencing of RNA isolated by crosslinking immunoprecipitation (HITS-CLIP). HITS-CLIP analysis of the neuron-specific splicing factor Nova2 revealed extremely reproducible RNA binding maps in multiple mouse brains. These maps provide genome-wide in vivo biochemical footprints confirming the previous prediction that the position of Nova binding determines the outcome of alternative splicing; moreover, they are sufficiently powerful to predict Nova action de novo. HITS-CLIP revealed a large number of Nova-RNA interactions in 3â UTRs, leading to the discovery that Nova regulates alternative polyadenylation in the brain. HITS-CLIP, therefore, provides a robust, unbiased means to identify functional protein-RNA interactions in vivo. Keywords: Comparative analysis Refer to individual Series. This SuperSeries is composed of the following subset Series: GSE17374: Wild type vs. Nova2 KO mouse: Exon array data GSE17376: Wild type vs. Nova2 KO mouse: Exon junction array data