Methods in molecular biology
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The protocol herein describes a robust and proven method for the measurement of pseudokinase-ligand interaction using a fluorescence-based thermal shift assay (TSA). Pseudokinases are kinase-like proteins that have recently emerged as crucial regulatory modules of signal transduction pathways and may well represent a novel class of drug targets. However, unlike kinases, the regulatory activity of pseudokinases is mainly conferred through protein-protein interactions. ⋯ Ligand binding to a protein is known to increase its thermal stability, which is reflected by a shift between the thermal denaturation curves of the unliganded protein and the liganded protein. Here, we illustrate the utility of the method with the pseudokinases, ErbB3/HER3, ILK, ROP5Bi, JAK1, JAK2, TYK2, MLKL, STRAD, TRIB1, VRK3, and ROR1. This method can also be used to determine optimal buffer conditions that may increase protein stability and can be tailored to other protein families.
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Recent advancements in high-throughput technologies such as mass spectrometry have led to an increase in the rate at which data is generated and accumulated. As a result, standard statistical methods no longer suffice as a way of analyzing such gigantic amounts of data. Network analysis, the evaluation of how nodes relate to one another, has over the years become an integral tool for analyzing high throughput proteomic data as they provide a structure that helps reduce the complexity of the underlying data. ⋯ These tools enable the visualization of proteins as networks of signaling, regulatory, and biochemical interactions. In this chapter, we provide an overview of networks and network theory fundamentals for the analysis of proteomics data. We further provide an overview of interaction databases and network tools which are frequently used for analyzing proteomics data.
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The bottom-up proteomic analysis of cell line and tissue samples to a depth > 10,000 proteins still represents a considerable challenge because of the sheer number of peptides generated by proteolytic digestions and the high dynamic range of protein expression. As a result, comprehensive protein coverage requires multidimensional peptide separation. ⋯ The protocol includes optimized sample preparation steps (lysis with the aid of mechanical disruption, one-step disulfide bridge reduction and alkylation), setup and operation of hSAX columns and gradients, desalting of hSAX fractions prior to LC-MS/MS analysis, and suggestions for the choice of data acquisition parameters and data analysis using MaxQuant. Application of the protocol to the fractionation of 300 μg human brain tissue digest led to the identification of more than 100,000 unique peptide sequences representing over 10,195 proteins and 9,500 genes in 3 days of measurement time on a Q Exactive Plus mass spectrometer.
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Extracellular vesicle (EV)-associated RNAs (EV-RNA) are under intense investigation due to their potential role in health and disease. Several approaches are currently employed to isolate blood-derived EVs for RNA analysis, most of which are either time-consuming and expensive, such as methods based on EVs physical properties (ultracentrifugation and Optiprep density gradient), or also copurify blood contaminants, mostly protein aggregates and immune complexes, (such as chemical precipitation). In addition, there is a lack of standardized protocols for the extraction of EV-RNA and very little consensus on the technological platforms and normalization tools for assessing the expression levels of different RNA species. ⋯ In this book chapter we propose a protocol that might overcome some of the abovementioned issues through antibody-based isolation of blood-derived EVs followed by extraction and expression analysis of small-RNA species (miRNA) by reverse transcriptase quantitative PCR (RT-qPCR). The advantages of immunoaffinity approaches over other isolation methods are multiple and include: (1) the selective enrichment of specific EV subpopulations with restricted tissue/cell origin, (2) reduction of matrix effects and blood contaminants that may confound miRNA profiling from complex biological fluids and (3) easy coupling to conventional quantitative assays (e.g., RT-qPCR). In conclusion, we describe a protocol for standard enrichment and quantitative analysis of EV-miRNAs from blood and we warrant for technological improvements, such as the use of novel biomaterials, surface chemistries, binding agents and assay/sensor design that may further improve it.
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Detection of Differential DNA Methylation Under Stress Conditions Using Bisulfite Sequence Analysis.
DNA methylation is the most important epigenetic change affecting gene expression in plants grown under normal as well as under stress conditions. Therefore, researchers study differential DNA methylation under distinct environmental conditions and their relationship with transcriptome abundance. Up to date, more than 25 methods and techniques are available to detect DNA methylation based on different principles. ⋯ This technique allows a single nucleotide resolution of 5-methylcytosine on a genome scale. WGBS technique workflow involves DNA fragmentation, processing through end blunting, terminal A(s) addition at 3' end and adaptor ligation, bisulfite treatment, PCR amplification, sequencing libraries and assembling, and finally alignment with the reference genome and data analysis. Despite the fact that WGBS is more reliable than the conventional clone-based bisulfite sequencing, it is costly, requires large amount of DNA and its output data is not easily handled.