Project description:In this study we developed a new assay to perform proximity biotinylation in cells without the requirement for genetic manipulation or transfection to fuse a biotin ligase to a protein of interest. We show the specificity by targeting H3K9me3 and performing ChIP-seq for the biotin modification. Targeting IgG was used as a control. By doing so, we identified flywch1 as a new protein binding to H3K9me3 regions, which we validated using ChIP-seq (IgG ChIP was used as a control)
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: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:Proximity biotinylation workflows typically require CRISPR-based genetic manipulation of target cells. To overcome this bottleneck, we fused the TurboID proximity biotinylation enzyme to Protein A. Upon target cell permeabilization, the ProtA-Turbo enzyme can be targeted to proteins of interest using an endogenous antibody against the bait protein. Addition of biotin then triggers bait-proximal protein biotinylation. Biotinylated proteins can subsequently be enriched from crude lysates and identified by mass spectrometry. We demonstrate this workflow by targeting Emerin, the histone modification H3K9me3 and the chromatin remodeler BRG1. Amongst the main findings, our experiments revealed Flywch1 as an essential protein that interacts with H3K9me3-marked centromeric heterochromatin. The ProtA-Turbo enzyme represents an ‘off the shelf’ proximity biotinylation enzyme that facilitates proximity biotinylation experiments in primary cells and can be used to understand how proteins cooperate in vivo and how this contributes to cellular homeostasis and disease.
Project description:Proximity biotinylation is a commonly used method to identify the in vivo proximal proteome for proteins of interest. This technology typically relies on fusing a bait protein to a biotin ligase using overexpression or CRISPR-based tagging, thus prohibiting such assays in (primary) cell types that are difficult to transfect. We recently developed an ‘off the shelf’ proximity biotinylation method, which makes use of a recombinant enzyme consisting of the biotin ligase TurboID fused to the antibody-recognizing moiety Protein A. In this method, a bait specific antibody and the ProteinA-Turbo enzyme are consecutively added to permeabilized fixed or unfixed cells. Following incubation, during which ProteinA-Turbo-antibody-antigen complexes are formed, unbound molecules are washed away, after which bait-proximal biotinylation is triggered by the addition of exogenous biotin. Finally, biotinylated proteins are enriched from crude lysates using streptavidin beads followed by mass spectrometry-based protein identification. Here, we present a detailed protocol for this method
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:Stress granules (SGs) are highly dynamic cytoplasmic membrane-less organelles that assemble when cells are challenged by stress. At different stages of assembly, various RNA molecules are sorted into SGs where they play important roles in maintaining the structural stability of SGs and regulating gene expression. Despite recent efforts of fluorescence microscopy and biochemical fractionation analysis, there still lacks a complete description of the dynamic changes in the molecular inventory of SG components during different stages of assembly and disassembly. In this study, we applied a proximity-dependent RNA labeling method, CAP-seq, to comprehensively investigate the content of local transcriptome in SGs, in the context of live mammalian cells. CAP-seq captures 457 and 822 RNAs in arsenite- and sorbitol-induced SGs in HEK293T cells, respectively, revealing that SG enrichment is positively correlated with RNA length and AU content, but negatively correlated with translation efficiency. The high spatial specificity of CAP-seq dataset is validated by single-molecule FISH imaging. We further applied CAP-seq profile RNA components in microscopically invisible SG cores, both before stress and after recovery from stress, thus mapping the dynamic changes in SG-proximal transcriptome along the time course of granule assembly/disassembly processes. Our data portray a model of AU-rich and translationally repressed SG nanostructure that are memorized long after the removal of stress.