Project description:Despite being predicted to lack coding potential, cytoplasmic long non-coding (lnc)RNAs can associate with ribosomes. However, the landscape and biological relevance of lncRNAs translation remains poorly studied. In yeast, cytoplasmic Xrn1-sensitive lncRNAs (XUTs) are targeted by the Nonsense-Mediated mRNA Decay (NMD), suggesting a translation-dependent degradation process. Here, we report that XUTs are pervasively translated, which impacts their decay. We show that XUTs globally accumulate upon translation elongation inhibition, but not when initial ribosome loading is impaired. Ribo-Seq confirmed ribosomes binding to XUTs and identified ribosome-associated 5’-proximal small ORFs. Mechanistically, the NMD-sensitivity of XUTs mainly depends on the 3’-untranslated region length. Finally, we show that the peptide resulting from the translation of an NMD-sensitive XUT reporter exists in NMD-competent cells. Our work highlights the role of translation in the post-transcriptional metabolism of XUTs. We propose that XUT-derived peptides could be exposed to the natural selection, while NMD restricts XUTs levels.
Project description:Antisense long non-coding (aslnc)RNAs represent a substantial part of eukaryotic transcriptomes that are, in yeast, controlled by the Xrn1 exonuclease. Nonsense-Mediated Decay (NMD) destabilizes the Xrn1-sensitive aslncRNAs (XUT), but what determines their sensitivity remains unclear. We report that 3’ single-stranded (3’-ss) extension mediates XUTs degradation by NMD, assisted by the Mtr4 and Dbp2 helicases. Single-gene investigation, genome-wide RNA analyses and double-stranded (ds)RNA mapping revealed that 3'-ss extensions discriminate the NMD-targeted XUTs from stable lncRNAs. Ribosome profiling showed that XUT are translated locking them for NMD activity. Interestingly, mutants of the Mtr4 and Dbp2 helicases accumulated XUTs, suggesting that dsRNA unwinding is a critical step for degradation. Indeed, expression of anti-complementary transcripts protects cryptic intergenic lncRNAs from NMD. Our results indicate that aslncRNAs form dsRNA that are only translated and targeted to NMD if dissociated by Mtr4 and Dbp2. We propose that NMD buffers genome expression by discarding pervasive regulatory transcripts.
Project description:Goal of the study is the identification of transcriptome deregulation of smg7 pad4 mutants, which are deficient in nonsense-mediated mRNA decay and are blocked in immune signaling, which should avoid secondary responses from immune signaling
Project description:Recessive retinitis pigmentosa (RP) is often caused by nonsense mutations that lead to low mRNA levels as a result of nonsense-mediated decay. Some RP genes are expressed at detectable levels in leukocytes as well as in the retina. We designed a microarray-based method to find recessive RP genes based on low lymphoblast mRNA expression levels Keywords: Recessive mutations; mRNA expression; nonsense mediated-decay; retinitis pigmentosa; lymphocyte; Affymetrix genechip Human Genome U133Plus2.0.
Project description:Goal of the study is the identification of transcriptome deregulation of smg7 pad4 mutants, which are deficient in nonsense-mediated mRNA decay and are blocked in immune signaling, which should avoid secondary responses from immune signaling Total RNA (ribosomal RNA depleted) illumina sequencing of three single end libraries respectively of adult pad4 leaves (control) vs adult smg7 pad4 mutant leaves (mutant)
Project description:We measured half-lives of 21,248 mRNA 3’ isoforms in yeast by rapidly depleting RNA polymerase II from the nucleus and performing direct RNA sequencing throughout the decay process. Interestingly, the half-lives of mRNA isoforms from the same gene, including nearly identical isoforms, often vary widely. Based on clusters of isoforms with different half-lives, we identify hundreds of sequences conferring stabilization or destabilization upon mRNAs terminating downstream. One class of stabilizing element is a polyU sequence that can interact with poly(A) tails, inhibit the association of poly(A) binding protein, and confer increased stability upon introduction into ectopic transcripts. More generally, destabilization and stabilization elements are linked to the degree to which the poly(A) tail can engage in double-stranded structures. Isoforms engineered to fold into 3’ stem-loop structures not involving the poly(A) tail exhibit even longer half-lives. We suggest that double-stranded structures at the 3’ ends are a major determinant of mRNA stability. Half-lives of 21,248 mRNA 3’ isoforms in yeast were measured by rapidly depleting RNA polymerase II from the nucleus and performing direct RNA sequencing throughout the decay process.
Project description:The Upf1, Upf2 and Upf3 proteins cooperate to implement nonsense-mediated decay. We used DNA microarrays for profiling RNA expression levels of upf2 and upf3 mutants
Project description:We have HA-tagged two nonsense-mediated decay proteins, UPF1 and UPF2, in the malaria parasite Plasmodium falciparum. We then performed co-immunoprecipitation experiments to determine the protein-protein interactions of these nonsense-mediated decay components.