Project description:We report a high resolution catalouge of NMD substrates using RNA-Seq. We discovered several hundred new substrates for NMD. Using published ribosome footprint profiling data, we measured ribosome densities of normal-looking NMD substrates and non-NMD substrates. NMD substrates exhibited a striking difference in normalized ribosome occupancy in wild-type and UPF1 cells. We also found that normal looking NMD substrates have higher ratio of out of frame reads, lower codon optimalites and a higher propensity to have long stretches of non-optimal codons.
Project description:Analysis of cellular SMD or NMD substrates that regulated by Upf1 and/or PNRC2 in HeLa cell. The hypothesis tested in the present study was that endogenous SMD or NMD substrates may co-regulated by Upf1 and PNRC2. Results provide important information that vast range of cellular SMD or NMD substrates are reqired PNRC2 for decay.
Project description:We aimed to study the cleavage sites of nonsense-mediated mRNA decay (NMD) substrates. Therefore, we depleted the major exoribonuclease XRN1 in human cell culture, which degrades the 3' fragments generated by SMG6-mediated endonucleolytic cleavage. Different reporter mRNAs or endogenous NMD targets were investigated and the 3' fragments were cloned, amplified and subsequently subjected to high throughput sequencing.
Project description:Analysis of cellular NMD (Nonsense-mediated mRNA decay) substrates that regulated by Upf1, SMG5, SMG7 and/or PNRC2 in HeLa cell. The hypothesis tested in the present study was that endogenous NMD substrates may co-regulated by Upf1, SMG5, SMG7 and PNRC2.
Project description:Analysis of cellular SMD or NMD substrates that regulated by Upf1 and/or PNRC2 in HeLa cell. The hypothesis tested in the present study was that endogenous SMD or NMD substrates may co-regulated by Upf1 and PNRC2. Results provide important information that vast range of cellular SMD or NMD substrates are reqired PNRC2 for decay. Total RNA obtained from HeLa cells with downregulation of Upf1 or PNRC2 by siRNA. The up- or down-regulated transcripts were compare to control siRNA treated HeLa cell RNA extract. Significant transcripts were confirmed by replication
Project description:The first round of translation occurs on mRNAs bound by nuclear cap-binding complex (CBC), which is composed of nuclear cap-binding protein (CBP) 80 and 20. During this round of translation, aberrant mRNAs are recognized and downregulated in abundance by nonsense-mediated mRNA decay (NMD), which is one of the mRNA quality control mechanisms. Here our microarray analysis reveals that the level of cyclin-dependent kinase inhibitor 1A (CDKN1A) mRNAs increases in the cells depleted of cellular NMD factors. Intriguingly, CDKN1A mRNA contains an upstream open reading frame (uORF), which is one of NMD-inducing features. Using chimeric reporter constructs and confocal microscopy, we find that the uORF of CDKN1A mRNA is actively translated and modulates a translational efficiency of the main downstream ORF. Our findings provide the biological insights into the possible role of NMD in diverse pathways mediated by CDKN1A. The microarray analysis performed to analize the cellular NMD substrates that regulated by Upf1, PNRC2 and/or CTIF in HeLa cell. The hypothesis tested in the present study was that endogenous NMD substrates may co-regulated by Upf1, PNRC2 and CTIF. Results provide important information that vast range of cellular NMD substrates are reqired CTIF.
Project description:Upf1, Upf2, and Upf3 are the central regulators of nonsense-mediated mRNA decay (NMD), the eukaryotic mRNA quality control pathway generally triggered when a premature termination codon is recognized by the ribosome. The NMD-related functions of the Upf proteins likely commence while these factors are ribosome-associated, but little is known of the timing of their ribosome binding, their specificity for ribosomes translating NMD substrates, or the nature and role of any ribosome:Upf complexes. Here, we have elucidated details of the ribosome-associated steps of NMD. By combining yeast genetics with selective ribosome profiling and co-sedimentation analyses of polysomes with wild-type and mutant Upf proteins, our approaches have identified distinct states of ribosome:Upf association. All three Upf factors manifest progressive polysome association as mRNA translation proceeds, but these events appear to be preceded by formation of a Upf1:80S complex as mRNAs initiate translation. This complex is likely executing an early mRNA surveillance function.
Project description:In metazoans, the endoribonuclease SMG6 is thought to cleave many endogenous mRNAs targeted for nonsense-mediated mRNA decay (NMD). However, most evidence as to the identity of endogenous SMG6 substrates is indirect, and little is known about their cleavage sites. Here, we report the efficacy of an RNA degradome approach called parallel analysis of RNA ends (PARE) for identifying NMD intermediates in human cells. By specifically sequencing the 5’ ends of intermediates dependent on SMG6 and the critical NMD factor UPF1, hundreds of endogenous transcripts that are direct targets of SMG6 have been revealed. A preferred sequence motif spanning most SMG6 cleavage sites has been identified and validated by mutational analysis. For many SMG6 substrates, depletion of SMG6 leads to decapping of the RNAs. These findings provide key insights into NMD and targeting by SMG6 while also demonstrating the potential of PARE for analyzing other ribonucleases with diverse endogenous substrates.
Project description:The first round of translation occurs on mRNAs bound by nuclear cap-binding complex (CBC), which is composed of nuclear cap-binding protein (CBP) 80 and 20. During this round of translation, aberrant mRNAs are recognized and downregulated in abundance by nonsense-mediated mRNA decay (NMD), which is one of the mRNA quality control mechanisms. Here our microarray analysis reveals that the level of cyclin-dependent kinase inhibitor 1A (CDKN1A) mRNAs increases in the cells depleted of cellular NMD factors. Intriguingly, CDKN1A mRNA contains an upstream open reading frame (uORF), which is one of NMD-inducing features. Using chimeric reporter constructs and confocal microscopy, we find that the uORF of CDKN1A mRNA is actively translated and modulates a translational efficiency of the main downstream ORF. Our findings provide the biological insights into the possible role of NMD in diverse pathways mediated by CDKN1A. The microarray analysis performed to analize the cellular NMD substrates that regulated by Upf1, PNRC2 and/or CTIF in HeLa cell. The hypothesis tested in the present study was that endogenous NMD substrates may co-regulated by Upf1, PNRC2 and CTIF. Results provide important information that vast range of cellular NMD substrates are reqired CTIF. Total RNA obtained from HeLa cells with downregulation of Upf1, PNRC2 or CTIF by siRNA. The up- or down-regulated transcripts were compare to control siRNA treated HeLa cell RNA extract. Significant transcripts were confirmed by replication.