DNA Baits Research Articles

Determining DNA-Protein Binding Affinities and Specificities from Crude Lysates Using a Combined SILAC/TMT Labeling Strategy.

In recent years, quantitative mass spectrometry-based interaction proteomics technology has proven very useful in identifying specific DNA-protein interactions using single pull-downs from crude lysates. Here, we applied a SILAC/TMT-based higher-order multiplexing approach to develop an interaction proteomics workflow called Protein-nucleic acid Affinity and Specificity quantification by MAss spectrometry in Nuclear extracts or PASMAN. In PASMAN, DNA pull-downs using a concentration range of specific and control DNA baits are performed in SILAC-labeled nuclear extracts. MS1-based quantification to determine specific DNA-protein interactions is then combined with sequential TMT-based quantification of fragmented SILAC peptides, allowing the generation of Hill-like curves and determination of apparent binding affinities. We benchmarked PASMAN using the SP/KLF motif and further applied it to gain insights into two CGCG-containing consensus DNA motifs. These motifs are recognized by two BEN domain-containing proteins, BANP and BEND3, which we find to interact with these motifs with distinct affinities. Finally, we profiled the BEND3 proximal proteome, revealing the NuRD complex as the major BEND3 proximal protein complex in vivo. In summary, PASMAN represents, to our knowledge, the first higher-order multiplexing-based interaction proteomics method that can be used to decipher specific DNA-protein interactions and their apparent affinities in various biological and pathological contexts.

Spatiotemporal and global profiling of DNA-protein interactions enables discovery of low-affinity transcription factors.

Precise dissection of DNA-protein interactions is essential for elucidating the recognition basis, dynamics and gene regulation mechanism. However, global profiling of weak and dynamic DNA-protein interactions remains a long-standing challenge. Here, we establish the light-induced lysine (K) enabled crosslinking (LIKE-XL) strategy for spatiotemporal and global profiling of DNA-protein interactions. Harnessing unique abilities to capture weak and transient DNA-protein interactions, we demonstrate that LIKE-XL enables the discovery of low-affinity transcription-factor/DNA interactions via sequence-specific DNA baits, determining the binding sites for transcription factors that have been previously unknown. More importantly, we successfully decipher the dynamics of the transcription factor subproteome in response to drug treatment in a time-resolved manner, and find downstream target transcription factors from drug perturbations, providing insight into their dynamic transcriptional networks. The LIKE-XL strategy offers a complementary method to expand the DNA-protein profiling toolbox and map accurate DNA-protein interactomes that were previously inaccessible via non-covalent strategies, for better understanding of protein function in health and disease.

Analytical validation and performance characteristics of a 48-gene next-generation sequencing panel for detecting potentially actionable genomic alterations in myeloid neoplasms.

Identification of genomic mutations by molecular testing plays an important role in diagnosis, prognosis, and treatment of myeloid neoplasms. Next-generation sequencing (NGS) is an efficient method for simultaneous detection of clinically significant genomic mutations with high sensitivity. Various NGS based in-house developed and commercial myeloid neoplasm panels have been integrated into routine clinical practice. However, some genes frequently mutated in myeloid malignancies are particularly difficult to sequence with NGS panels (e.g., CEBPA, CARL, and FLT3). We report development and validation of a 48-gene NGS panel that includes genes that are technically challenging for molecular profiling of myeloid neoplasms including acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and myeloproliferative neoplasms (MPN). Target regions were captured by hybridization with complementary biotinylated DNA baits, and NGS was performed on an Illumina NextSeq500 instrument. A bioinformatics pipeline that was developed in-house was used to detect single nucleotide variations (SNVs), insertions/deletions (indels), and FLT3 internal tandem duplications (FLT3-ITD). An analytical validation study was performed on 184 unique specimens for variants with allele frequencies ≥5%. Variants identified by the 48-gene panel were compared to those identified by a 35-gene hematologic neoplasms panel using an additional 137 unique specimens. The developed assay was applied to a large cohort (n = 2,053) of patients with suspected myeloid neoplasms. Analytical validation yielded 99.6% sensitivity (95% CI: 98.9–99.9%) and 100% specificity (95% CI: 100%). Concordance of variants detected by the 2 tested panels was 100%. Among patients with suspected myeloid neoplasms (n = 2,053), 54.5% patients harbored at least one clinically significant mutation: 77% in AML patients, 48% in MDS, and 45% in MPN. Together, these findings demonstrate that the assay can identify mutations associated with diagnosis, prognosis, and treatment options of myeloid neoplasms even in technically challenging genes.

Performance comparison of four types of target enrichment baits for exome DNA sequencing

BackgroundNext-generation sequencing technology is developing rapidly and target capture sequencing has become an important technique. Several different platforms for library preparation and target capture with different bait types respectively are commercially available. Here we compare the performance of the four platforms with different bait types to find out their advantages and limitations. The purpose of this study is to help investigators and clinicians select the appropriate platform for their particular application and lay the foundation for the development of a better target capture platform for next-generation sequencing.ResultsWe formulate capture efficiency as a novel parameter that can be used to better evaluations of specificity and coverage depth among the different capture platforms. Target coverage, capture efficiency, GC bias, AT Dropout, sensitivity in single nucleotide polymorphisms, small insertions and deletions detection, and the feature of each platform were compared for low input samples. In general, all platforms perform well and small differences among them are revealed. In our results, RNA baits have stronger binding power than DNA baits, and with ultra deep sequencing, double stranded RNA baits perform better than single stranded RNA baits in all aspects. DNA baits got better performance in the region with high GC content and RNA baits got lower AT dropout suggesting that the binding power is different between DNA and RNA baits to genome regions with different characteristics.ConclusionsThe platforms with double stranded RNA baits have the most balanced capture performance. Our results show the key differences in performance among the four updated platforms with four different bait types. The better performance of double stranded RNA bait with ultra deep sequencing suggests that it may improve the sensitivity of ultra low frequent mutation detection. In addition, we further propose that the mixed baits of double stranded RNA and single stranded DNA may improve target capture performance.

SarA plays a predominant role in controlling the production of extracellular proteases in the diverse clinical isolates of Staphylococcus aureus LAC and UAMS-1

SUMMARY Using DNA affinity chromatography we demonstrate that the S. aureus regulatory proteins MgrA, Rot, SarA, and SarS bind DNA baits derived from the promoter regions associated with the genes encoding aureolysin, ScpAB, SspABC, and SplA-F. Three of four baits also bound SarR and SarZ, the exception in both cases being the ScpAB-associated bait. Using the USA300, methicillin-resistant strain LAC and the USA200, methicillin-sensitive strain UAMS-1, we generated mutations in the genes encoding each of these proteins alone and in combination with sarA and examined the impact on protease production, the accumulation of high molecular weight proteins, and biofilm formation. These studies confirmed that multiple regulatory loci are involved in limiting protease production to a degree that impacts all of these phenotypes, but also demonstrate that sarA plays a predominant role in this regard. Using sarA mutants unable to produce individual proteases alone and in combination with each other, we also demonstrate that the increased production of aureolysin and ScpA is particularly important in defining the biofilm-deficient phenotype of LAC and UAMS-1 sarA mutants, while aureolysin alone plays a key role in defining the reduced accumulation of alpha toxin and overall cytotoxicity as assessed using both osteoblasts and osteoclasts.

Hybridization ddRAD-sequencing for population genomics of nonmodel plants using highly degraded historical specimen DNA.

Species' responses at the genetic level are key to understanding the long-term consequences of anthropogenic global change. Herbaria document such responses, and, with contemporary sampling, provide high-resolution time-series of plant evolutionary change. Characterizing genetic diversity is straightforward for model species with small genomes and a reference sequence. For nonmodel species-with small or large genomes-diversity is traditionally assessed using restriction-enzyme-based sequencing. However, age-related DNA damage and fragmentation preclude the use of this approach for ancient herbarium DNA. Here, we combine reduced-representation sequencing and hybridization-capture to overcome this challenge and efficiently compare contemporary and historical specimens. Specifically, we describe how homemade DNA baits can be produced from reduced-representation libraries of fresh samples, and used to efficiently enrich historical libraries for the same fraction of the genome to produce compatible sets of sequence data from both types of material. Applying this approach to both Arabidopsis thaliana and the nonmodel plant Cardamine bulbifera, we discovered polymorphisms de novo in an unbiased, reference-free manner. We show that the recovered genetic variation recapitulates known genetic diversity in A. thaliana, and recovers geographical origin in both species and over time, independent of bait diversity. Hence, our method enables fast, cost-efficient, large-scale integration of contemporary and historical specimens for assessment of genome-wide genetic trends over time, independent of genome size and presence of a reference genome.

Evaluation of a 42-Gene Next-Generation Sequencing Panel for Detection of Acute Myeloid Leukemia Mutations for Clinical Use

Abstract Objectives Identification of genetic alterations by molecular and cytogenetic testing has an important role in the classification, risk stratification, and management of acute myeloid leukemia (AML). We evaluated a next-generation sequencing (NGS) panel that assesses IDH2, FLT3, NPM1, and TP3 and 38 other genes associated with diagnostic, prognostic, and/or therapeutic utility in AML, with a turnaround time of 8 to 14 days, using a DNA input of 50 ng. Methods In total, 110 patients, 65 males and 45 females, at a median age of 58 years (range: 2-68 years) with clinical diagnosis of AML were included in this study. Targeted regions were captured by hybridization with complementary biotinylated DNA baits, and NGS was performed on an Illumina NextSeq500 instrument. Sequence reads were analyzed using a bioinformatics pipeline that was developed in house. Analytical sensitivity of the assay is ~5% mutated alleles with 100% specificity. Results A total of 296 pathogenic mutations in 38 genes were detected in 95 of 110 samples (86%). On average, three mutations (range 1-10) were detected per positive sample. Variant frequency ranged from 3.0% to 96.1%. Most frequently mutated genes were TET2 (18.2%), FLT3 (18.2%), TP53 (17.3%), RUNX1 (15.5%), NPM1 (14.5%), ASXL1 (12.7%), NRAS (11.8%), and CEBPA (10.9%). In total, 166 of 296 (56%) mutations from 13 genes had prognostic significance, 42 of 296 (14%) mutations from three genes (CEBPA, NPM1, RUNX1) had diagnostic significance, and 40 of 296 (14%) mutations from three genes (IDH1, IDH2, FLT3) had therapeutic significance. Conclusion This focused 42-gene targeted panel identifies mutations of clinical significance in over 85% of patients with a clinical diagnosis of AML.

Analytical validation of a 47-gene NGS panel for molecular profiling of myeloid neoplasms.

e18526 Background: Molecular profiling can help diagnose, classify, and guide treatment of myeloid neoplasms. Next generation sequencing (NGS) is a powerful platform that can facilitate identification of actionable genetic alterations in multiple genes simultaneously. To serve clinical management needs, we developed and validated a NGS panel for 47 genes associated with diagnostic, prognostic, and/or therapeutic utilities for each of the subclasses of myeloid neoplasms: acute myeloid leukemia (AML, 42 genes), myelodysplastic syndrome (MDS, 36 genes), and myeloproliferative neoplasms (MPN, 26 genes). Methods: A total of 154 unique de-identified specimens were analyzed. Intra- and inter-assay precision studies were performed by standard laboratory practice. Single nucleotide variations (SNVs), insertions/deletions (indels), and FLT3 partial tandem duplications (PTD) were assessed for the entire coding regions of 23 genes and targeted exons of 24 genes. Target regions were captured by hybridization with complementary biotinylated DNA baits, and NGS was performed on an Illumina NextSeq500 instrument. Sequence reads obtained were analyzed using a bioinformatics pipeline that was developed in-house. At least 500 unique reads with base quality (Q) ≥20 (99% confidence) were required for coverage QC, except targets on X chromosome for male specimens, which required 250 unique reads. Results: On average, each sample generated 13.2 million reads, 100% (SD = 0.2%) mapped reads to the reference sequence, 61.7% (SD = 8.8%) on-target reads, and 1,952 (SD = 873) mean coverage. Data using ≥Q20 unique coverage of all target regions across all validation samples demonstrated that all target regions, even in the extreme end of GC spectrum (range: 12%-87%), met coverage requirements. Intra- and inter-assay precision studies, using 7 and 21 specimens, respectively, resulted in 100% concordance among replicates. An accuracy study of 131 unique specimens (a subset of the 154 specimens) yielded in 99.6% (755/758, 95% CI: 99.4%-100%) concordance for variants with allele frequencies ≥5% in comparison to other molecular methods including Sanger sequencing. No reportable variants were detected from any normal specimens (n = 17). Conclusions: We developed and validated a NGS panel for 47 genes with diagnostic, prognostic, and/or therapeutic utilities for each of the subclasses of myeloid neoplasms: AML (42 genes), MDS (36 genes), and MPN (26 genes). This panel will allow simultaneous analysis of the 47 genes with high sensitivity and specificity and may help manage clinical needs.

Cost‐efficient high throughput capture of museum arthropod specimen DNA using PCR‐generated baits

Abstract Gathering genetic data for rare species is one of the biggest remaining obstacles in modern phylogenetics, particularly for megadiverse groups such as arthropods. Next generation sequencing techniques allow for sequencing of short DNA fragments contained in preserved specimens >20 years old, but approaches such as whole‐genome sequencing are often too expensive for projects including many taxa. Several methods of reduced representation sequencing have been proposed that lower the cost of sequencing per specimen, but many remain costly because they involve synthesizing nucleotide probes and target hundreds of loci. These datasets are also frequently unique for each project and thus generally incompatible with other similar datasets. Here, we explore utilization of in‐house generated DNA baits to capture commonly utilized mitochondrial and ribosomal DNA loci from insect museum specimens of various ages and preservation types without the a priori need to know the sequence of the target loci. Both within species and cross‐species capture are explored, on preserved specimens ranging in age from one to 54 years old. We found most samples produced sufficient amounts of data to assemble the nuclear ribosomal rRNA genes and near complete mitochondrial genomes and produce well‐resolved phylogenies in line with expected results. The dataset obtained can be straightforwardly combined with the large cache of existing Sanger‐sequencing‐generated data built up over the past 30 years and targeted loci can be easily modified to those commonly used in different taxa. Furthermore, the protocol we describe allows for inexpensive data generation (as low as ~$35/sample), of at least 20 kilobases per specimen, for specimens at least as old as ~1965, and can be easily conducted in most laboratories. If widely applied, this technique will accelerate the accurate resolution of the Tree of Life especially on non‐model organisms with limited existing genomic resources.

Application of Solid-State Capture for the Retrieval of Small-to-Medium Sized Target Loci from Ancient DNA.

Genetic studies that include ancient samples are often hampered by the low amount of endogenous DNA that ancient samples often contain, relative to co-extracted "contaminant" DNA from other organisms. One approach to mitigate this challenge is to perform hybridization-based capture of target genomic regions using DNA or RNA baits. Such baits are designed to have high sequence similarity to the target genomic regions and can reduce the off-target fraction in DNA sequencing libraries. Here, we present a protocol to use Agilent SureSelect microarrays to enrich ancient DNA libraries for small-to-medium-sized target loci, such as mitochondrial genomes, from ancient DNA extracts. The protocol that we present builds on previously published work by introducing improvements that improve recovery of short DNA fragments while minimizing the cost and duration of the experiment.

Whole-Genome Capture of Ancient DNA Using Homemade Baits.

For many archaeological and paleontological samples, the relative content of endogenous compared to contaminant DNA is low. In such cases, enriching sequencing libraries for endogenous DNA, prior to sequencing can make the final research project more cost-effective. Here, we present an in-solution enrichment protocol based on homemade baits that can be applied to recover complete nuclear genomes from ancient remains. The approach is based on the preparation of DNA baits by biotinylated adapter ligation. The procedure has been developed for use with human remains but can be adapted to other species or target regions by choosing the appropriate template DNA from which to build the capture baits. By using homemade rather than commercially acquired baits, this protocol may offer increased flexibility and cost efficiency.

Ultrasensitive Detection of Circulating Tumor DNA in Lymphoma via Targeted Hybridization Capture and Deep Sequencing of Barcoded Libraries.

Liquid biopsies are rapidly emerging as powerful tools for the early detection of cancer, noninvasive genomic profiling of localized or metastatic tumors, prompt detection of treatment resistance-associated mutations, and monitoring of therapeutic response and minimal residual disease in patients during clinical follow-up. Growing evidence strongly supports the utility of circulating tumor DNA (ctDNA) as a biomarker for the stratification and clinical management of lymphoma patients. However, ctDNA is diluted by variable amounts of cell-free DNA (cfDNA) shed by nonneoplastic cells causing a background signal of wild-type DNA that limits the sensitivity of methods that rely on DNA sequencing. Here, we describe an error suppression method for single-molecule counting that relies on targeted sequencing of cfDNA libraries constructed with semi-degenerate barcode adapters. Custom pools of biotinylated DNA baits for target enrichment can be designed to specifically track somatic mutations in one patient, survey mutation hotspots with diagnostic and prognostic value or be comprised of comprehensive gene panels with broad patient coverage in lymphoma. Such methods are amenable to track ctDNA levels during longitudinal liquid biopsy testing with high specificity and sensitivity and characterize, in real time, the genetic profiles of tumors without the need of standard invasive biopsies. The analysis of ultra-deep sequencing data according to the bioinformatics pipelines also described in this chapter affords to harness lower limits of detection for ctDNA below 0.1%.

Global profiling of protein\u2013DNA and protein\u2013nucleosome binding affinities using quantitative mass spectrometry

Interaction proteomics studies have provided fundamental insights into multimeric biomolecular assemblies and cell-scale molecular networks. Significant recent developments in mass spectrometry-based interaction proteomics have been fueled by rapid advances in label-free, isotopic, and isobaric quantitation workflows. Here, we report a quantitative protein–DNA and protein–nucleosome binding assay that uses affinity purifications from nuclear extracts coupled with isobaric chemical labeling and mass spectrometry to quantify apparent binding affinities proteome-wide. We use this assay with a variety of DNA and nucleosome baits to quantify apparent binding affinities of monomeric and multimeric transcription factors and chromatin remodeling complexes.

Screening Arrayed Libraries with DNA and Protein Baits to Identify Interacting Proteins.

Molecular interactions are an integral part of the regulatory mechanisms controlling gene expression. The yeast one- and two-hybrid systems (Y1H/Y2H) have been widely used by many laboratories to detect DNA-protein (Y1H) and protein-protein interactions (Y2H). The development of efficient cloning systems have promoted the generation of large open reading frame (ORF) clone collections (libraries) for several organisms. Functional analyses of such large collections require the establishment of adequate protocols. Here, we describe a simple straightforward procedure for high-throughput screenings of arrayed libraries with DNA or protein baits that can be carried out by one person with minimal labor and not requiring robotics. The protocol can also be scaled up or down and is compatible with several library formats. Procedures to make yeast stocks for long-term storage (tube and microplate formats) are also provided.

Yeast One- and Two-Hybrid High-Throughput Screenings Using Arrayed Libraries.

Since their original description more than 25 years ago, the yeast one- and two-hybrid systems (Y1H/Y2H) have been used by many laboratories to detect DNA-protein (Y1H) and protein-protein interactions (Y2H). These systems use yeast cells (Saccharomyces cerevisiae) as a eukaryotic "test tube" and are amenable for most labs in the world. The development of highly efficient cloning methods has fostered the generation of large collections of open reading frames (ORFs) for several organisms that have been used for yeast screenings. Here, we describe a simple mating based method for high-throughput screenings of arrayed ORF libraries with DNA (Y1H) or protein (Y2H) baits not requiring robotics. One person can easily carry out this protocol in approximately 10 h of labor spread over 5 days. It can also be scaled down to test one-to-one (few) interactions, scaled up (i.e., robotization) and is compatible with several library formats (i.e., 96, 384-well microtiter plates).

Proteomics to study DNA-bound and chromatin-associated gene regulatory complexes.

High-resolution mass spectrometry (MS)-based proteomics is a powerful method for the identification of soluble protein complexes and large-scale affinity purification screens can decode entire protein interaction networks. In contrast, protein complexes residing on chromatin have been much more challenging, because they are difficult to purify and often of very low abundance. However, this is changing due to recent methodological and technological advances in proteomics. Proteins interacting with chromatin marks can directly be identified by pulldowns with synthesized histone tails containing posttranslational modifications (PTMs). Similarly, pulldowns with DNA baits harbouring single nucleotide polymorphisms or DNA modifications reveal the impact of those DNA alterations on the recruitment of transcription factors. Accurate quantitation – either isotope-based or label free – unambiguously pinpoints proteins that are significantly enriched over control pulldowns. In addition, protocols that combine classical chromatin immunoprecipitation (ChIP) methods with mass spectrometry (ChIP-MS) target gene regulatory complexes in their in-vivo context. Similar to classical ChIP, cells are crosslinked with formaldehyde and chromatin sheared by sonication or nuclease digested. ChIP-MS baits can be proteins in tagged or endogenous form, histone PTMs, or lncRNAs. Locus-specific ChIP-MS methods would allow direct purification of a single genomic locus and the proteins associated with it. There, loci can be targeted either by artificial DNA-binding sites and corresponding binding proteins or via proteins with sequence specificity such as TAL or nuclease deficient Cas9 in combination with a specific guide RNA. We predict that advances in MS technology will soon make such approaches generally applicable tools in epigenetics.

Gateway-Compatible Yeast One-Hybrid Screens

INTRODUCTIONProtein-DNA interactions (PDIs) between transcription factors (TFs) and their target genes form the backbone of transcription regulatory networks. Such PDIs can be identified with either a TF or a gene as a starting point. The Gateway-compatible yeast one-hybrid (Y1H) system provides a high-throughput, gene-centered method for the identification of interactions between a "DNA bait" (e.g., cis-regulatory DNA elements or gene promoters) and "protein preys" (e.g., TFs). The Y1H system is a genetic system to detect PDIs based on selection of reporter gene expression in yeast. DNA baits are fused by Gateway cloning to two reporter genes, HIS3 and lacZ, and the resulting DNA bait::reporter constructs are subsequently integrated into the genome of the host yeast strain. After integration, baits are examined for self-activation (i.e., their ability to drive reporter gene expression in the absence of an exogenous prey protein). Subsequently, each DNA bait is screened for interacting proteins by transforming a library of preys into the corresponding Y1H DNA bait yeast strain. Preys are hybrid proteins composed of a protein from the organism of interest and a heterologous transcription activation domain. When a prey protein binds to the DNA bait, the heterologous activation domain activates reporter gene expression. Thus, physical interactions between both repressors and activators and their DNA targets can be identified.

A gateway-compatible yeast one-hybrid system.

Since the advent of microarrays, vast amounts of gene expression data have been generated. However, these microarray data fail to reveal the transcription regulatory mechanisms that underlie differential gene expression, because the identity of the responsible transcription factors (TFs) often cannot be directly inferred from such data sets. Regulatory TFs activate or repress transcription of their target genes by binding to cis-regulatory elements that are frequently located in a gene's promoter. To understand the mechanisms underlying differential gene expression, it is necessary to identify physical interactions between regulatory TFs and their target genes. We developed a Gateway-compatible yeast one-hybrid (Y1H) system that enables the rapid, large-scale identification of protein-DNA interactions using both small (i.e., DNA elements of interest) and large (i.e., gene promoters) DNA fragments. We used four well-characterized Caenorhabditis elegans promoters as DNA baits to test the functionality of this Y1H system. We could detect approximately 40% of previously reported TF-promoter interactions. By performing screens using two complementary libraries, we found novel potentially interacting TFs for each promoter. We recapitulated several of the Y1H-based protein-DNA interactions using luciferase reporter assays in mammalian cells. Taken together, the Gateway-compatible Y1H system will allow the high-throughput identification of protein-DNA interactions and may be a valuable tool to decipher transcription regulatory networks.