Project description:5’ ExoSeq of total RNA (rRNA & signal recognition particle RNA depleted) from mouse cortical neurons before and after membrane depolarization by potassium chloride (KCl).
Project description:We generated Bscl2lox/lox mice X ERT2-Adipoq-CRE mice, allowing inducible seipin deletion in adipocytes upon tamoxifen addition (iATSKO). Indeed, a 5-day tamoxifen treatment led to a dramatic decrease in Bscl2 mRNA in the adipose tissue. To study the effects of seipin deficiency in vivo on adipose tissue homeostasis in an unbiased manner, we used 3’-signal recognition particle (SRP) RNA sequencing.
Project description:Mitochondria from subcutaneous white adipose tissues of control or signal recognition particle 54c (SPR54c) transgenic mice were isolated and underwent further Percoll gradient-based purification. Purified mitochondria were subject to mass-spectrometry based proteomic analysis performed by UT Southwestern Proteomics Core. ID# 696496: SRP54c Transgenic; ID# 696497: control.
Project description:To test whether non-coding RNAs play roles in regulating response to powdery mildew infection and heat stress in wheat, by using Solexa high-throughput sequencing and computational analysis and experimental approach we cloned the small RNAs and identified 125 putative long npcRNAs from wheat leaves infected by preponderant physiological strain Erysiphe graminis f. sp. tritici (Egt) or by heat stress treatment. Among long non-coding RNAs, some were precursors of small RNAs such as microRNAs and siRNAs, two long npcRNAs were identified as signal recognition particle (SRP) 7S RNA variants, and three were characterized as U3 snoRNAs. Wheat long npcRNAs showed tissue dependent expression patterns and were responsive to powdery mildew infection and heat stress.
Project description:The signal recognition particle (SRP) enables cotranslational delivery of proteins for translocation into the endoplasmic reticulum (ER), but its full in vivo role remains incompletely explored. We combined rapid auxin-induced SRP degradation with proximity-specific ribosome profiling to define SRP’s in vivo function in yeast. Despite the classic view that SRP recognizes amino-terminal signal sequences, we show that SRP was generally essential for targeting transmembrane domains regardless of their position relative to the amino-terminus. By contrast, many proteins containing cleavable amino-terminal signal peptides were efficiently cotranslationally targeted in SRP’s absence. We also reveal an unanticipated consequence of SRP loss: Transcripts normally targeted to the ER were mistargeted to mitochondria, leading to mitochondrial defects. These results elucidate SRP’s essential roles in maintaining the efficiency and specificity of protein targeting.
Project description:Salivary gland-specific binding assays reveal that CrebA, a bZIP transcription factor, directly binds the vast majority of genes encoding the secretory machinery, including proteins of the signal recognition particle and receptor, proteins involved in co-translational import of cargo into the ER, proteins involved in vesicular transport between the ER and Golgi, as well as the structural proteins and enzymes of these organelles. CrebA does not bind salivary gland-specific cargo genes. Instead, it binds and boosts expression of Sage, which encodes a bHLH transcription factor that upregulates cargo expression. CrebA also directly binds and upregulates Xbp1, which encodes a key factor in the unfolded protein response, and Tudor-SN, which encodes a protein that in other systems increases secretory cargo mRNA levels.
Project description:Cotranslational targeting into the endoplasmic reticulum (ER) by the Signal Recognition Particle (SRP) is a key event determining polypeptide fate in eukaryotic cells. Here, we globally define the principles and mechanisms of SRP binding and ER targeting in vivo. Cotranslational targeting through SRP is the dominant route into the ER for all secretory proteins, regardless of targeting signal characteristics. Cytosolic SRP functions in a pioneer translation round that builds a membrane-resident mRNAs pool, explaining how low SRP levels suffice for the secretory load. SRP does not induce an elongation arrest; consequently, kinetic competition between targeting and translation elongation dictates which substrates are translocated post-translationally. Unexpectedly, SRP binds most secretory ribosomal complexes before targeting signals are synthesized. We show non-coding mRNA elements can promote signal-independent SRP pre-recruitment. Our study defines the complex kinetic interplay between elongation and determinants in the polypeptide and mRNA modulating SRP-substrate selection and membrane targeting in vivo.
Project description:Cotranslational targeting into the endoplasmic reticulum (ER) by the Signal Recognition Particle (SRP) is a key event determining polypeptide fate in eukaryotic cells. Here, we globally define the principles and mechanisms of SRP binding and ER targeting in vivo. Cotranslational targeting through SRP is the dominant route into the ER for all secretory proteins, regardless of targeting signal characteristics. Cytosolic SRP functions in a pioneer translation round that builds a membrane-resident mRNAs pool, explaining how low SRP levels suffice for the secretory load. SRP does not induce an elongation arrest; consequently, kinetic competition between targeting and translation elongation dictates which substrates are translocated post-translationally. Unexpectedly, SRP binds most secretory ribosomal complexes before targeting signals are synthesized. We show non-coding mRNA elements can promote signal-independent SRP pre-recruitment. Our study defines the complex kinetic interplay between elongation and determinants in the polypeptide and mRNA modulating SRP-substrate selection and membrane targeting in vivo. Ribosome profiling (RiboSeq) and RNA-seq of subcellular fractions of ribosomes. Soluble and membrane bound ribosomes are separated by centrifugation, and SRP-bound ribosomes are immunoprecipitated from the soluble fraction. Polysomes and monosomes are separated by sucrose gradient ultracentrifugation.
Project description:Spatial organization of the transcriptome has emerged as a powerful means for regulating the post-transcriptional fate of RNA in eukaryotes; however, whether prokaryotes use RNA spatial organization as a mechanism for post-transcriptional regulation remains unclear. Here we used super-resolution microscopy to image the E. coli transcriptome and observed a genome-wide spatial organization of RNA: mRNAs encoding inner-membrane proteins are enriched at the membrane, whereas mRNAs encoding outer-membrane, cytoplasmic and periplasmic proteins are distributed throughout the cytoplasm. Membrane enrichment is caused by co-translational insertion of signal peptides recognized by the signal-recognition particle. Our time-resolved RNA-sequencing and live-cell super-resolution imaging experiments revealed a physiological consequence of this spatial organization and the underlying mechanism: membrane localization enhances degradation rates of inner-membrane-protein mRNAs by placing them in proximity to membrane-bound RNA degradation enzymes. Together, these results demonstrate that the bacterial transcriptome is spatially organized and that this organization shapes the posttranscriptional Spatial organization of the transcriptome has emerged as a powerful means for regulating the post-transcriptional fate of RNA in eukaryotes; however, whether prokaryotes use RNA spatial organization as a mechanism for post-transcriptional regulation remains unclear. Here we used super-resolution microscopy to image the E. coli transcriptome and observed a genome-wide spatial organization of RNA: mRNAs encoding inner-membrane proteins are enriched at the membrane, whereas mRNAs encoding outer-membrane, cytoplasmic and periplasmic proteins are distributed throughout the cytoplasm. Membrane enrichment is caused by co-translational insertion of signal peptides recognized by the signal-recognition particle. Our time-resolved RNA-sequencing and live-cell super-resolution imaging experiments revealed a physiological consequence of this spatial organization and the underlying mechanism: membrane localization enhances degradation rates of inner-membrane-protein mRNAs by placing them in proximity to membrane-bound RNA degradation enzymes. Together, these results demonstrate that the bacterial transcriptome is spatially organized and that this organization shapes the post-transcriptional dynamics of mRNAs.
Project description:Various pathways can target nascent or fully synthesized precursor polypeptides to the human endoplasmic reticulum (ER). Typically, they involve cytosolic proteins or complexes and their respective receptors on the ER surface. The signal recognition particle (SRP) and the heterodimeric SRP-receptor (SR) represent one such targeting system, others are TRC40 and its heterodimeric TRC-receptor (WRB/CAML) and the components of the SND pathway. Apparently, they all can target precursor polypeptides to the Sec61-channel in the ER membrane. To characterize the substrate specificities of these targeting pathways, we combined siRNA-mediated depletion of membrane receptor subunits in HeLa cells with label-free quantitative proteomics and differential protein abundance analyis.