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This document provides a list of references and citations from scientific articles on plant development, protein interactions, and ubiquitin ligases. The articles cover topics such as the role of F-box proteins in plant development, the identification of protein substrates using mass spectrometry, and the use of proximity labeling techniques to study molecular interactions in plants. [Extracted from the article]

SUMMARY: The cytosol‐facing outer membrane (OM) of organelles communicates with other cellular compartments to exchange proteins, metabolites, and signaling molecules. Cellular surveillance systems also target OM‐resident proteins to control organellar homeostasis and ensure cell survival under stress. However, the OM proximity proteomes have never been mapped in plant cells since using traditional approaches to discover OM proteins and identify their dynamically interacting partners remains challenging. In this study, we developed an OM proximity labeling (OMPL) system using biotin ligase‐mediated proximity biotinylation to identify the proximity proteins of the OMs of mitochondria, chloroplasts, and peroxisomes in living Arabidopsis (Arabidopsis thaliana) cells. Using this approach, we mapped the OM proximity proteome of these three organelles under normal conditions and examined the effects of the ultraviolet‐B (UV‐B) or high light (HL) stress on the abundances of OM proximity proteins. We demonstrate the power of this system with the discovery of cytosolic factors and OM receptor candidates potentially involved in local protein translation and translocation. The candidate proteins that are involved in mitochondrion–peroxisome, mitochondrion–chloroplast, or peroxisome–chloroplast contacts, and in the organellar quality control system are also proposed based on OMPL analysis. OMPL‐generated OM proximity proteomes are valuable sources of candidates for functional validation and suggest directions for further investigation of important questions in cell biology. [ABSTRACT FROM AUTHOR]

Protein clustering is a ubiquitous event in diverse cellular processes. Self‐association of proteins triggers recruitment of downstream proteins to regulate cellular signaling. To investigate the interactions in detail, chemical biology tools to identify proteins recruited to defined assemblies are required. Here, we exploit an identification of proteins recruited in artificial granules (IPRAG) platform that combines intracellular Y15‐based supramolecule construction with a proximity labeling method. We validated the IPRAG tool using Nck1 as a target bait protein. We constructed Nck1‐tethering granules, labeled the recruited proteins with biotin, and analyzed them by LC‐MS/MS. As a result, we successfully identified proteins that directly or indirectly interact with Nck1. [ABSTRACT FROM AUTHOR]

Protein‐protein interactions (PPIs) play critical roles in almost all cellular signal transduction events. Characterization of PPIs without interfering with the functions of intact cells is very important for basic biology study and drug developments. However, the ability to profile PPIs especially those weak/transient interactions in their native states remains quite challenging. To this end, many endeavors are being made in developing new methods with high efficiency and strong operability. By coupling with advanced fluorescent microscopy and mass spectroscopy techniques, these strategies not only allow us to visualize the subcellular locations and monitor the functions of protein of interest (POI) in real time, but also enable the profiling and identification of potential unknown interacting partners in high‐throughput manner, which greatly facilitates the elucidation of molecular mechanisms underlying numerous pathophysiological processes. In this review, we will summarize the typical methods for PPIs identification in living cells and their principles, advantages and limitations will also be discussed in detail. [ABSTRACT FROM AUTHOR]

Many cellular functions are carried out by protein pairs or families, providing robustness alongside functional diversity. For such processes, it remains a challenge to map the degree of specificity versus promiscuity. Protein–protein interactions (PPIs) can be used to inform on these matters as they highlight cellular locals, regulation and, in cases where proteins affect other proteins ‐ substrate range. However, methods to systematically study transient PPIs are underutilized. In this study, we create a novel approach to systematically compare stable or transient PPIs between two yeast proteins. Our approach, Cel‐lctiv (CELlular biotin‐Ligation for Capturing Transient Interactions in vivo), uses high‐throughput pairwise proximity biotin ligation for comparing PPIs systematically and in vivo. As a proof of concept, we studied the homologous translocation pores Sec61 and Ssh1. We show how Cel‐lctiv can uncover the unique substrate range for each translocon allowing us to pinpoint a specificity determinator driving interaction preference. More generally, this demonstrates how Cel‐lctiv can provide direct information on substrate specificity even for highly homologous proteins. Synopsis: Protein‐protein interactions (PPIs) can reveal information about cellular localization, regulation, and substrate range of protein pairs or families. A new biotin ligation approach allows systematic study and comparison of stable and transient PPIs in vivo. The Cel‐lctiv (CELlular biotin‐Ligation for Capturing Transient Interactions in vivo) method systematically compares stable or transient PPIs between yeast proteins.Cel‐lctiv uses high‐throughput, pairwise proximity‐biotin ligation in vivo.Proof‐of‐concept application of Cel‐lctiv to the homologous translocation pores Sec61 and Ssh1 defines their unique substrate ranges.Cel‐lctiv uncovers a unique signal peptide feature that differentiates Sec61 and Ssh1 substrates. [ABSTRACT FROM AUTHOR]

Cilia are microtubule‐based organelles that protrude from the cell surface and play crucial roles in cellular signaling pathways and extracellular fluid movement. Defects in the ciliary structures and functions are implicated in a set of hereditary disorders, including polycystic kidney disease, nephronophthisis, and Bardet–Biedl syndrome, which are collectively termed as ciliopathies. The application of mass spectrometry‐based proteomic approaches to explore ciliary components provides important clues for understanding their physiological and pathological roles. In this review, we focus primarily on proteomic studies involving the identification of proteins in motile cilia and primary cilia, proteomes in ciliopathies, and interactomes of ciliopathy proteins. Collectively, the integration of these data sets will be beneficial for the comprehensive understanding of ciliary structures and exploring potential biomarkers and therapeutic targets for ciliopathies. [ABSTRACT FROM AUTHOR]

Structural and functional analyses of proteins‐of‐interest (POI) in multimolecular crowding conditions (mMCC) such as live cells and tissues are regarded as inevitable challenges for in depth understanding of the real shapes of POIs in their existing natural environments. Activity‐based protein profiling (ABPP) is a definitely powerful tool capable of analyzing a proteome possessing a particular activity under mMCC. While ABPP usually targets a proteome of interest, study of a particular protein in mMCC is also valuable. Although activity‐based probes (ABPs) are often used for this aim, most of conventional ABPs cause the loss of original activities, and therefore are not perfectly suitable for functional analysis of labeled proteins. Ligand‐directed chemistry (LDchem) developed by our group is an alternative approach of ABPs, that can modify a surface of POI rather than its active site using a cleavable electrophile in a traceless manner. LDchem thus enables the POI labeling with a synthetic fluorophore with no or minimal effects on the original functions of POIs even in mMCC. In this review, we briefly describe a principle of LDchem for native protein labeling and summarize its recent chemical biology applications such as the imaging‐based biological analysis of POI functions and construction of POI‐based biosensors. [ABSTRACT FROM AUTHOR]

Fluorescein-tagged proteins are first purified using anti-fluorescein-based immunoprecipitation of the lysate followed by streptavidin coated bead-based pull-down of the first eluate resulting in the enrichment of doubly-labeled proteins, corresponding to their presence in both donor and acceptor compartments. Keywords: new methodology; proximity labeling; TransitID EN new methodology proximity labeling TransitID 546 548 3 10/25/23 20231101 NES 231101 TransitID is a new methodology based on proximity labeling allowing for the study of protein trafficking a the proteome scale. These purified proteins can then be analyzed using tandem mass spectrometry. gl First, the proteome in a donor compartment (localization #1, Figure 1) is biotin-labeled with a compartment-resident TurboID-tagged protein. [Extracted from the article]

Proximity labeling techniques are emerging high‐throughput methods for studying protein‐protein, protein‐RNA, and protein‐DNA interactions with temporal and spatial precision. Proximity labeling methods take advantage of enzymes that can covalently label biomolecules with reactive substrates. These labeled biomolecules can be identified using mass spectrometry or next‐generation sequencing. The main advantage of these methods is their ability to capture weak or transient interactions between biomolecules. Proximity labeling is indispensable for studying organelle interactomes. Additionally, it can be used to resolve spatial composition of macromolecular complexes. Many of these methods have only recently been introduced; nonetheless, they have already provided new and deep insights into the biological processes at the cellular, organ, and organism levels. In this paper, we review a broad range of proximity labeling techniques, their development, drawbacks and advantages, and implementations in recent studies. [ABSTRACT FROM AUTHOR]

A better understanding of the molecular mechanisms underlying disease is key for expediting the development of novel therapeutic interventions. Disease mechanisms are often mediated by interactions between proteins. Insights into the physical rewiring of protein–protein interactions in response to mutations, pathological conditions, or pathogen infection can advance our understanding of disease etiology, progression, and pathogenesis and can lead to the identification of potential druggable targets. Advances in quantitative mass spectrometry (MS)‐based approaches have allowed unbiased mapping of these disease‐mediated changes in protein–protein interactions on a global scale. Here, we review MS techniques that have been instrumental for the identification of protein–protein interactions at a system‐level, and we discuss the challenges associated with these methodologies as well as novel MS advancements that aim to address these challenges. An overview of examples from diverse disease contexts illustrates the potential of MS‐based protein–protein interaction mapping approaches for revealing disease mechanisms, pinpointing new therapeutic targets, and eventually moving toward personalized applications. [ABSTRACT FROM AUTHOR]

The spatial arrangement of chromosome within the nucleus is linked to genome function and gene expression regulation. Existing genome‐wide mapping methods often rely on chemically crosslinking DNA with protein baits, which raises concerns of artifacts being introduced during cell fixation. By genetically targeting a photosensitizer protein to specific subnuclear locations, we achieved blue‐light‐activated labeling of local DNA with a bioorthogonal functional handle for affinity purification and sequence identification through next‐generation sequencing. When applied to the nuclear lamina in human embryonic kidney 293T cells, it revealed lamina‐associated domains (LADs) that cover 37.6 % of the genome. These LADs overlap with heterochromatin hallmarks and are depleted with CpG islands. This simple labeling method avoids the harsh treatment of chemical crosslinking and is generally applicable to the genome‐wide high‐resolution mapping of the spatial chromosome organization in living cells. [ABSTRACT FROM AUTHOR]

Enzyme‐catalyzed proximity labeling (PL) with the engineered ascorbate peroxidase APEX2 is a novel approach to map organelle compartmentalization and protein networks in living cells. Current procedures developed for mammalian cells do not allow delivery of the cosubstrate, biotin‐phenol, into living yeast cells. Here, we present a new method based on semipermeabilized yeast cells. Combined with stable isotope labeling by amino acids in cell culture (SILAC), we demonstrate proteomic mapping of a membrane‐enclosed and a semiopen compartment, the mitochondrial matrix and the nucleus. APEX2 PL revealed nuclear proteins that were previously not identified by conventional techniques. One of these, the Yer156C protein, is highly conserved but of unknown function. Its human ortholog, melanocyte proliferating gene 1, is linked to developmental processes and dermatological diseases. A first characterization of the Yer156C neighborhood reveals an array of proteins linked to proteostasis and RNA binding. Thus, our approach establishes APEX2 PL as another powerful tool that complements the methods palette for the model system yeast. [ABSTRACT FROM AUTHOR]

RNA biology is orchestrated by the dynamic interactions of RNAs and RNA‐binding proteins (RBPs). In the present study, we describe a new method of proximity‐dependent protein labeling to detect RNA–protein interactions [RNA‐bound protein proximity labeling (RBPL)]. We selected the well‐studied RNA‐binding protein PUF to examine the current proximity labeling enzymes birA* and APEX2. A new version of birA*, BASU, was used to validate that the PUF protein binds its RNA motif. We further optimized the RBPL labeling system using an inducible expression system. The RBPL (λN‐BASU) labeling experiments exhibited high signal‐to‐noise ratios. We subsequently determined that RBPL (λN‐BASU) is more suitable than RBPL (λN‐APEX2) for the detection of RNA–protein interactions in live cells. Interestingly, our results also reveal that proximity labeling is probably capable of biotinylating proximate nascent peptide. [ABSTRACT FROM AUTHOR]

APEX2, an engineered ascorbate peroxidase for high activity, is a powerful tool for proximity labeling applications. Owing to its lack of disulfides and the calcium‐independent activity, APEX2 can be applied intracellularly for targeted electron microscopy imaging or interactome mapping when fusing to a protein of interest. However, APEX2 fusion is often deleterious to the protein expression, which seriously hampers its wide utility. This problem is especially compelling when APEX2 is fused to structurally delicate proteins, such as multi‐pass membrane proteins. In this study, we found that a cysteine‐free single mutant C32S of APEX2 dramatically improved the expression of fusion proteins in mammalian cells without compromising the enzyme activity. We fused APEX2 and APEX2C32S to four multi‐transmembrane solute carriers (SLCs), SLC1A5, SLC6A5, SLC6A14, and SLC7A1, and compared their expressions in stable HEK293T cell lines. Except the SLC6A5 fusions expressing at decent levels for both APEX2 (70%) and APEX2C32S (73%), other three SLC proteins showed significantly better expression when fusing to APEX2C32S (69 ± 13%) than APEX2 (29 ± 15%). Immunofluorescence and western blot experiments showed correct plasma membrane localization and strong proximity labeling efficiency in all four SLC‐APEX2C32S cells. Enzyme kinetic experiments revealed that APEX2 and APEX2C32S have comparable activities in terms of oxidizing guaiacol. Overall, we believe APEX2C32S is a superior fusion tag to APEX2 for proximity labeling applications, especially when mismatched disulfide bonding or poor expression is a concern. [ABSTRACT FROM AUTHOR]

The subcellular organization of biomolecules such as proteins and nucleic acids is intimately linked to their biological functions. APEX2, an engineered ascorbate peroxidase that enables proximity‐dependent labeling of proteins in living cells, has emerged as a powerful tool for deciphering the molecular architecture of various subcellular structures. However, only phenolic compounds have thus far been employed as APEX2 substrates, and the resulting phenoxyl radicals preferentially react with electron‐rich amino acid residues. This narrow scope of substrates could potentially limit the application of APEX2. In this study, we screened a panel of aromatic compounds and identified biotin‐conjugated arylamines as novel probes with significantly higher reactivity towards nucleic acids. As a demonstration of the spatial specificity and depth of coverage in mammalian cells, we applied APEX2 labeling with biotin‐aniline (Btn‐An) in the mitochondrial matrix, capturing all 13 mitochondrial messenger RNAs and none of the cytoplasmic RNAs. APEX2‐mediated Btn‐An labeling of RNA is thus a promising method for mapping the subcellular transcriptome, which could shed light on its functions in cell physiology. [ABSTRACT FROM AUTHOR]

Protein-protein interactions, living cells, fluorescence, proximity labeling, enzyme, photoactivation Keywords: protein-protein interactions; living cells; fluorescence; proximity labeling; enzyme; photoactivation EN protein-protein interactions living cells fluorescence proximity labeling enzyme photoactivation 1 1 1 07/19/23 20230717 NES 230717 B Elucidation of Protein-Protein Interactions (PPIs) b in living cells/animals is very important for the study of basic biology and the development of novel therapeutics. Front Cover: Chemical and Biological Strategies for Profiling Protein-Protein Interactions in Living Cells (Chem. [Extracted from the article]

Primary cilia are sensory, antennae-like organelles present on the surface of many cell types. They have been involved in a variety of diseases collectively termed ciliopathies. As cilia are essential regulators of cell signaling, the composition of the ciliary membrane needs to be strictly regulated. To understand regulatory processes at the ciliary membrane, we report the targeting of a genetically engineered enzyme specifically to the ciliary membrane to allow biotinylation and identification of the membrane-associated proteome. Bioinformatic analysis of the comprehensive dataset reveals high-stoichiometric presence of actin-binding proteins inside the cilium. Immunofluorescence stainings and complementary interaction proteomic analyses confirm these findings. Depolymerization of branched F-actin causes further enrichment of the actin-binding and actin-related proteins in cilia, including Myosin 5a (Myo5a). Interestingly, Myo5a knockout decreases ciliation while enhanced levels of Myo5a are observed in cilia upon induction of ciliary disassembly. In summary, we present a novel approach to investigate dynamics of the ciliary membrane proteome in mammalian cells and identify actin-binding proteins as mechanosensitive components of cilia that might have important functions in cilia membrane dynamics. [ABSTRACT FROM AUTHOR]

The biotin identification (BioID) protocol uses a mutant of the biotin ligase BirA (BirA*) fused to a protein-of-interest to biotinylate proximate proteins in intact cells. Here, we show that two inactive halves of BirA* separately fused to a catalytic and regulatory subunit of protein phosphatase PP1 reconstitute a functional BirA* enzyme upon heterodimerization of the phosphatase subunits. We also demonstrate that this BirA* fragment complementation approach, termed split-BioID, can be used to screen for substrates and other protein interactors of PP1 holoenzymes. Split-BioID is a novel and versatile tool for the identification of (transient) interactors of protein dimers. [ABSTRACT FROM AUTHOR]

Biotin ligase, DamID, DNA-protein interactions, mass spectrometry, peroxidase, photosensitizer, protein- protein interactions, proximity labeling, PUP-IT, RNA-protein interactions, TRIBE Keywords: biotin ligase; DamID; DNA-protein interactions; mass spectrometry; peroxidase; photosensitizer; protein- protein interactions; proximity labeling; PUP-IT; RNA-protein interactions; TRIBE EN biotin ligase DamID DNA-protein interactions mass spectrometry peroxidase photosensitizer protein- protein interactions proximity labeling PUP-IT RNA-protein interactions TRIBE 1 1 1 01/20/22 20220117 NES 220117 B Proximity labeling b is a multi-tool approach suitable for analyzing protein-protein, protein-RNA, and protein-DNA interactions with temporal and spatial precision. Front Cover: Proximity Labeling Techniques: A Multi-Omics Toolbox (Chem. [Extracted from the article]