Project description:We have developed Halo-seq, an RNA proximity labeling method that allows the quantification of subcellular transcriptomes. We have demonstrated the efficacy of Halo-seq here by using it to quantify chromatin-proximal, nucleolar, and cytoplasmic transcriptomes. In Halo-seq, RNA molecules in close proximity to a spatially restricted protein are specifically marked and biotinylated, facilitating their separation from bulk cellular RNA and their quantification.
Project description:The vertebrate brain consists of diverse neuronal types, classified by distinct anatomy and function, along with divergent transcriptomes and proteomes. Defining the cell-type specific neuroproteome is important for understanding the development and functional organization of neural circuits. This task remains challenging in complex tissue, due to suboptimal protein isolation techniques that often result in loss of cell-type specific information and incomplete capture of subcellular compartments. Here, we develop a genetically targeted proximity labeling approach to identify cell-type specific subcellular proteome in the mouse brain, confirmed by imaging, electron microscopy, and mass spectrometry. We express subcellular-localized APEX2 to map the proteome of direct and indirect pathway spiny projection neurons in the striatum. The workflow provides sufficient depth to uncover changes in the proteome of striatal neurons following activation of Gαq-coupled signaling cascades. This method enables flexible, cell-type specific quantitative profiling of subcellular proteome snapshots in the mouse brain.
Project description:In eukaryotic cells, the subcellular targeting of RNA controls many fundamental aspects of cellular physiology. RNA molecules are broadly distributed throughout the nucleoplasm and cytoplasm, but are conventionally believed to be excluded from the secretory pathway compartments, including the endoplasmic reticulum (ER). Recent discovery of RNA N-glycan modification (glycoRNAs) has challenged this view, but direct evidence of RNA localization in the ER lumen has been lacking. In this study, we applied enzyme-mediated proximity labeling to profile the ER lumen-localized RNAs in human embryonic kidney 293T cells and rat cortical neurons. Our dataset revealed the presence of small non-coding RNAs in the ER lumen, including U RNAs, sco/sca RNAs and Y RNAs, which partially overlap with glycoRNAs. These findings shed light on novel RNA targeting mechanism and raise interesting questions regarding the biological functions of ER lumenal RNAs.
Project description:Many cellular RNAs localize to specific subcellular compartments. Currently, methods to systematically study subcellular RNA localization are limited and lagging behind proteomic approaches. Here, we combined APEX2-mediated proximity biotinylation of proteins with PAR-CLIP to simultaneously profile the proteome and the transcriptome bound by RNA binding proteins in any given subcellular compartment. Our approach is fractionation-independent and does not rely on additional RNA manipulation and labeling steps, thus making it easy to apply. Furthermore, it enables to study the locali-zation of RNA processing intermediates, as well as the identification of regulatory RNA cis-acting elements occupied in different cellular compartments. In a proof-of-concept study we studied RNA and protein localization in the nucleus, cytoplasm and at cell-cell interfaces using Proximity-CLIP. These experiments revealed among other in-sights frequent transcriptional readthrough continuing for several kilobases down-stream of the canonical cleavage and polyadenylation site, a differential binding pat-tern of nuclear and cytoplasmic mRNAs, as well as the localization of mRNAs contain-ing 3’UTR CUG sequence elements at cell-cell interfaces, of which many encode regulatory proteins.
Project description:This proof-of-principle experiment was designed to demonstrate the feasibility of proximity labeling for RNAM-bM-^@M-^Sprotein interactions IPL-seq on 293T-Rex expressing MSA-SNRPN70 (sample) or NFH-SNRPN70 (control)
Project description:Across cell types and organisms, thousands of RNAs display asymmetric subcellular distributions. The study of this process often requires quantifying abundances of specific RNAs at precise subcellular locations. To analyze subcellular transcriptomes, multiple proximity-based techniques have been developed in which RNAs near a localized bait protein are specifically labeled, facilitating their biotinylation and purification. However, these complex methods are often laborious and require expensive enrichment reagents. To streamline the analysis of localized RNA populations, we developed Oxidation-Induced Nucleotide Conversion sequencing (OINC-seq). In OINC-seq, RNAs near a genetically encoded, localized bait protein are specifically oxidized in a photo-controllable manner. These oxidation events are then directly detected and quantified using high-throughput sequencing and our software package, PIGPEN, without the need for biotin-mediated enrichment. We demonstrate that OINC-seq can induce and quantify RNA oxidation with high specificity in a dose- and light-dependent manner. We further show the spatial specificity of OINC-seq by using it to quantify subcellular transcriptomes associated with the cytoplasm, ER, and the inner and outer membranes of mitochondria. Finally, using transgenic zebrafish, we demonstrate that OINC-seq allows proximity-mediated RNA labeling in live animals. In sum, OINC-seq together with PIGPEN provide an accessible workflow for the analysis of localized RNAs across different biological systems.
Project description:HEK293T cells expressing BS2 in different compartments (cytosol, mitochondria, nucleus, nucleolus) were labeled with AC-2. Subsequent enrichment of labeled RNAs, PolyA capture and RNA-seq reveals RNA populations in those compartments.
Project description:In situ profiling of subcellular proteomic networks in primary and living systems, such as primary cells from native tissues or clinic samples, is crucial for the understanding of life processes and diseases, yet challenging for the current proximity labeling methods (e.g., BioID, APEX) due to their necessity of genetic engineering. Here we report CAT-S, a state-of-the-art bioorthogonal photocatalytic chemistry-enabled proximity labeling method, that expands proximity labeling to a wide range of primary living samples for in situ profiling of subcellular proteomes. Powered by the newly introduced thioQM labeling warhead and targeted bioorthogonal photocatalytic decaging chemistry, CAT-S enables labeling of mitochondrial proteins in living cells with high efficiency and specificity (up to 87%). We applied CAT-S to diverse cell cultures, mouse tissues as well as primary T cells from human blood, portraying the native-state mitochondrial proteomic characteristics, and unveiled a set of hidden mitochondrial proteins in human proteome. Furthermore, CAT-S allows quantitative analysis of the in situ proteomic perturbations on dysfunctional tissue samples, exampled by diabetic mouse kidneys, and revealed the alterations of lipid metabolism machinery that drive the disease progression. Given the advantages of non-genetic operation, generality, efficiency as well as spatiotemporal resolution, CAT-S may open new avenues as a proximity labeling strategy for in situ investigation of subcellular proteomic landscape of primary living samples that are otherwise inaccessible.