Systematic identification of G-quadruplex sensitive lethality by genome-wide genetic screening
ABSTRACT: A375 and HT1080 cells are treated with G-quadruplex ligands PDS or PhenDC3 following genome-wide shRNA knockdown. This enables the identification of genes that when silenced, specifically compromises cell growth in the presence of the ligand. First, a pilot screen was performed to determine a ligand concentration and experimental duration that caused ligand-specific, significant changes in shRNA levels. Second, a genome-wide screen was performed to globally evaluate G4-ligand synthetic lethal interactions. Third, to corroborate the G4-sensitisers uncovered in the genome-wide screen, a focussed screen was performed with a custom shRNA pool.
Project description:Dynamic acetylation of metabolic proteins has emerged as a ubiquitous post-translational modification of human metabolic proteins. However, the corresponding modifying enzymes and the functions of the modification await exploration. Using a genome-wide synthetic lethality screen, we constructed a genetic interaction network of human histone deacetylases (HDACs) and discovered many metabolic substrates of these enzymes. We further confirmed that the adenosine monophosphate-activated protein kinase (AMPK) catalytic subunit is acetylated and deacetylated by EP300 and HDAC1, respectively. Deacetylation of AMPK catalytic subunit enhances physical interaction with the upstream kinase LKB1, and leads to AMPK phosphorylation and activation. These findings highlight the importance of genetic interaction profiling to identify specific substrates of individual HDACs and elucidate how cells use protein (de)acetylation to coordinate nutrient availability and cellular energy status. To study the functional specificity of individual HDAC, we developed a genome-wide genetic interaction profiling technology in cultured human cells by RNAi using pooled TRC (The RNAi Consortium) 75k human shRNA library and complexity deconvolution by high-density microarray with a half-hairpin barcode design. The HCT116 colon cancer cell line was chosen as the screen platform because of its quasinormal diploid karyotype. The performance of the customized microarray we designed was first evaluated by the receiver operating characteristic (ROC) curve showing high sensitivity (89%), specificity (94%) and area under curve (0.95), as well as a control hybridization without DNA sample showing low background signal. Both results suggest that the fluorescent signals were generated by specific hybridization reactions. The high correlation of signal between Cy5 and Cy3 channel as well as dye-swap experiments indicated that biases between the two labeling fluorophores during competitive hybridization were negligible. Moreover, correlation between technical and biological replicates confirmed the high reproducibility of the methodology. In the screen, we used stable polyclonal cells expressing shRNA constructs targeting firefly luciferase (shLuciferase) as control. We checked the knockdown efficiency in protein or RNA level of individual shRNA constructs for 12 human HDAC genes (HDAC1~4, HDAC6~9, SIRT1~3 and SIRT5) by immunoblotting or quantitative PCR, and generated stable polyclonal query cell lines expressing two shRNA constructs with the highest knockdown efficiency for each HDAC gene. After transduction by TRC shRNA lentiviral pools, benchmark samples were harvested prior to puromycin selection, and the remaining cells were propagated under selection and harvested again after 18 population doublings as the end samples. Half-hairpin barcode library of the benchmark and end samples was recovered from genomic DNA respectively by PCR with Cy5 and Cy3-labeled primers, gel purified, and hybridized to the microarray. For each shRNA construct, the Z-score of the log2(Cy5/Cy3) was computed, and Z-score difference was calculated by subtracting the Z-score of the control sample from that of the query sample. Z-score differences larger than 1.5 and less than -1.5 were used as arbitrary thresholds to define candidate negative and positive genetic interactions, respectively.
Project description:Acute myeloid leukemia (AML) is characterized by a marked genetic heterogeneity, which complicates the development of novel therapeutics. The delineation of pathways essential within the patient-individual mutational background might overcome this limitation and facilitate personalized treatment. We report the results of a large-scale lentiviral loss-offunction RNA-interference-(RNAi)-screen in primary leukemic cells. Stringent validation identified six genes (BNIPL1, ROCK1, RPS13, STK3, SNX27, WDHD1) whose knockdown impaired growth and viability of the cells. Dependence on these genes was not caused by mutation or overexpression and while some of the candidates seemed to be rather patientspecific, others were essential in cells isolated from other AML patients. In addition to the phenotype observed after ROCK1 knockdown, treatment with the approved ROCK-inhibitor fasudil resulted in increased apoptosis and decreased viability of primary AML cells. In contrast to observations in some other malignancies, ROCK1-inhibition did not foster growth of immature malignant progenitors; but was also toxic to this cell fraction in feeder-co-culture and xenotransplantion experiments, indicating a distinct effect of ROCK1 inhibition on leukemic progenitors. We conclude that large scale RNAi screens in primary patient-derived cells are feasible and can complement other methods for personalized cancer therapies, such as expression and mutation profiling. Large-scale lentiviral loss-of-function shRNA screen in primary leukemic cells with two time points, exome sequencing of primary leukemic cells, and a gene expression profiling of primary cells from four leukemic and three healthy samples.
Project description:Rosiglitazone (rosi) is a powerful insulin sensitizer, but serious toxicities have curtailed its widespread clinical use. Rosi functions as a high-affinity ligand for PPARg, the adipocyte-predominant nuclear receptor (NR). The classic model, involving binding of ligand to the NR on DNA, explains positive regulation of gene expression, but ligand-dependent repression is not well understood. We have now addressed this issue by studying the direct effects of rosiglitazone on gene transcription, using global run-on sequencing (GRO-seq). Rosi-induced changes in gene body transcription were pronounced after 10 minutes and correlated with steady-state mRNA levels as well as with transcription at nearby enhancers (eRNAs). Upregulated eRNAs occurred almost exclusively at PPARg binding sites, to which rosi treatment recruited the coactivator MED1. By contrast, transcriptional repression by rosi involved a loss of MED1 from eRNA sites devoid of PPARg and enriched for other TFs including AP-1 factors and C/EBPs. Thus, rosi activates and represses transcription by fundamentally different mechanisms that could inform the future development of antidiabetic drugs. 3T3-L1 matuer adipocyte were treated with rosi, and nascent transcripts were measured at various time points using GRO-seq. ChIP-seq experiments for various coactivators, corepressor, and transcription factors also have been done to monitor initial occupancy or change before and after treatment.
Project description:The hallmark of human cancer is heterogeneity, mirroring the complexity of genetic and epigenetic alterations acquired during oncogenesis. We extracted DNA of 14 cultured human ovarian carcinoma cell lines subjected to pooled shRNA screen using TRC 1.0 library, and performed DNAseq. 14 ovarian carcinoma cell lines DNAseq data.
Project description:We have previously shown that some gefitinib insensitive head and neck squamous cell carcinoma (HNSCC) cell lines exhibit dominant autocrine fibroblast growth factor receptor (FGFR) signaling. Herein, we deployed a whole genome loss-of-function screen to identify genes whose knockdown potentiated the inhibitory effect of the FGFR inhibitor, AZ12908010, in HNSCC cell lines. Three HNSCC cell lines expressing a genome-wide shRNA library were treated with AZ8010 and the abundance of shRNA sequences was assessed by deep sequencing. Synthetic lethal hits were validated through use of specific inhibitors and independent shRNAs. We found that multiple alternate receptors provided protection from FGFR inhibition, including the receptor tyrosine kinases (RTKs), epidermal growth factor receptor 2 (ERBB2) and hepatocyte growth factor receptor (MET). We showed that specific knockdown of either ERBB2 or MET in combination with FGFR inhibition led to increased inhibition of growth relative to FGFR tyrosine kinase inhibitor (TKI) treatment alone. These results were confirmed using specific small molecule inhibitors of either ERBB family members or MET. Moreover, the combination of FGFR, MET and ERBB family inhibitors showed the largest inhibition of growth as compared to the double combinations. These results reveal a role for alternate RTKs in maintaining pro-growth and survival signaling in HNSCC cells in the setting of FGFR inhibition. Thus, improved therapies for HNSCC patients could involve rationally designed combinations of TKIs targeting FGFR, ERBB family members and MET. Using a genome-wide shRNA library in combination with deep sequencing, we screened for gene targets that were synthetic lethal with the FGFR inhibitor, AZ12908010 in HNSCC cells. Three HNSCC cell lines were screened in triplicate and the abundance of shRNA sequences in drug treated cells was compared to control treated cells.
Project description:Background: Recent advances in single-cell techniques have provided the opportunity to finely dissect cellular heterogeneity within populations previously defined by “bulk” assays and to uncover rare cell types. In human hematopoiesis, megakaryocytes and erythroid cells differentiate from a shared precursor, the megakaryocyte-erythroid progenitor (MEP), which remains poorly defined.Results: To clarify the cellular pathway in erythro-megakaryocyte differentiation, we correlated the surface immunophenotype, transcriptional profile and differentiation potential of individual MEP cells. Highly purified, single MEP cells (n=681) were analyzed using index fluorescence-activated cell sorting with parallel targeted transcriptional profiling of the same cells performed using a specifically designed panel of 87 genes. Differentiation potential was tested in novel, single-cell differentiation assays. Our results demonstrated that immunophenotypic MEP in fact comprise three distinct subpopulations: (1) “Pre-MEP”, enriched for erythroid/megakaryocyte progenitors but with residual myeloid differentiation capacity (2) “E-MEP”, strongly biased towards erythroid differentiation, and (3) “MK-MEP”, a previously undescribed, rare population of cells that are bipotent but primarily generate megakaryocytic progeny. Therefore, conventionally-defined MEP are in fact a mixed population: a minority give rise to mixed-lineage colonies while the majority of cells are transcriptionally-primed to generate exclusively single-lineage output. Conclusions: Our study clarifies the cellular hierarchy in human megakaryocyte/erythroid lineage commitment and highlights the importance of using a combination of single-cell approaches to dissect cellular heterogeneity and identify rare cell types within a population. We present a novel immunophenotyping strategy that enables the prospective identification of specific intermediate progenitor populations in erythro-megakaryopoiesis, allowing for in-depth study of disorders including inherited cytopenias, myeloproliferative disorders and erythromegakaryocytic leukemias. Multiplex RT-PCR gene expression profiling of 807 human megakaryocyte-erythroid progenitor cells (MEP) isolated from three healthy donors by apheresis following G-CSF treatment. Cells were excluded if more than 70 assays did not result in amplification or displayed Ct higer than 13 for B2M or higher than 15 for GAPDH. Furthermore cells with a mean non-dropout Ct value greater than 20 were removed. This resulted in a dataset of 681 cells, which were subsequently normalised to the mean of B2M and GAPDH expression.
Project description:In recent years, due to the influence of climate change and rising sea temperature, the incidence of Vibrio alginolyticus infections is increasing, and becoming the second most common Vibrio species reported in human illness. Therefore, better understanding of the pathogenic mechanism of V. alginolyticus infection is urgently needed. Vvrr1 (Vibrio virulence regulatory RNA 1) is a new found ncRNA predicted to be closely related to the adhesion ability of V. alginolyticus through the previous RNA-seq. In this study, the target genes of Vvrr1 were fully screened and verified by constructing Vvrr1 over-expressed strains and proteome sequencing technology.
Project description:To identify which mRNAs bind to RBM4/HIF-2a Two PAR-CLIPs were performed: One of an RBM4 immunoprecipitation, and the other of a HIF-2a immunoprecipitation and excising the associated RBM4 band.
Project description:Ptf1a is a lineage-specific basic-helix-loop-helix transcription factor critical in the development of both the pancreas and nervous system. How one transcription factor controls diverse programs of gene expression is a fundamental question in developmental biology. To uncover molecular strategies for the program-specific functions of Ptf1a, we identified bound genomic regions in vivo during development of both tissues. A majority of regions bound by Ptf1a are tissue-specific, lie near genes needed for proper formation and maturation of each tissue, and reflect regions of open chromatin. Information for the specificity of Ptf1a binding and function is encoded in the DNA surrounding the Ptf1a-bound sites, since Ptf1a-bound regions are sufficient to direct tissue-restricted reporter expression when tested in transgenic mice. Fox and Sox factors were identified as lineage specific modifiers of Ptf1a binding, since binding motifs for these factors are enriched in Ptf1a-bound regions in pancreas and neural tube, respectively. Although Ptf1a and Foxa2 co-localize to sites in embryonic pancreas and can act synergistically in cell transfection assays, biochemical experiments detected no physical interaction between the two factors. These findings indicate that lineage-specific chromatin landscapes likely constrain the functions of Ptf1a, and identify Fox and Sox gene families as part of this process. RNA-Seq: Examination of gene expression in Ptf1a expressing cells (NT E.12.5, Pancreas E15.5) ChIP-Seq: Examination of chromatin occupancy in 2 tissue types (E12.5 NT and 17.5 Pancreas). Faire-Seq: Examination of open chromatin in 2 tissue types (E12.5 NT and 17.5 Pancreas).
Project description:Transcriptional profiles during all phases of growth of Salmonella Typhimurium SL1344 were obtained and used to investigate growth phase-dependent alterations in gene expression. Viable count growth curve analysis of the growth system showed a culture lag time of 2.09 hours, and profiles at 4, 20, 40, 60, 90 and 120 minutes were measured accordingly. For comparison, profiles of the inoculum (0 min), mid-exponential (380 min), late-exponential (630 min), early-stationary (900 min) and late-stationary phase (2880 min) were also obtained. Large-scale gene-expression changes were seen, with substantial changes within 4 minutes of inoculation, indicating the speed and sophistication at which Salmonella senses its new environment during lag phase. Timecourse; 46 samples (11 timepoints, each with two biological replicates and at least two technical replicates); each sample hybridised in a two-channel hybridization against Salmonella genomic DNA as the comparator/reference, which also acted as a control for spot quality.