Project description:Genome-wide mapping of transcription factor binding is generally performed by chemical protein-DNA crosslinking, followed by chromatin immunoprecipitation and deep sequencing (ChIP-seq). Here we present the ChIP-seq technique based on photochemical crosslinking of protein-DNA interactions by high-intensity ultraviolet (UV) laser irradiation in living mammalian cells (UV-ChIP-seq). UV laser irradiation induces efficient and instant formation of covalent “zero-length” crosslinks exclusively between nucleic acids and proteins that are in immediate contact, thus resulting in a “snapshot” of direct protein-DNA interactions in their natural environment. We applied UV-ChIP-seq for genome-wide profiling of the sequence-specific transcriptional repressor B-cell lymphoma 6 (BCL6) in human diffuse large B-cell lymphoma (DLBCL) cells. Our approach resulted in sensitive and precise protein-DNA binding profiles, highly enriched in canonical BCL6 DNA sequence motifs. UV-ChIP-seq also revealed numerous previously undetectable BCL6 binding sites, particularly in more condensed, inaccessible areas of chromatin.
Project description:Regulation of gene expression is essential for normal development and cellular growth. Transcriptional events are tightly controlled both spatially and temporally by specific DNA-protein interactions. In this study we finely map the genome-wide targets of the CREB protein across all known and predicted human promoters, and characterize the functional consequences of a subset of these binding events using high-throughput reporter assays. To measure CREB binding, we used HaloCHIP, an antibody-free alternative to the ChIP method that utilizes the HaloTag fusion protein, and also high-throughput promoter-luciferase reporter assays, which provide rapid and quantitative screening of promoters for transcriptional activation or repression in living cells. CREB ChIP-chip two biologcal replicates. HaloCHIP-chip three biological replicates with and without Forskolin
Project description:Ultra-violet (UV) and high-intensity visible (VIS) radiation are environmental stressors known to harm photosynthetic organisms through the generation of reactive intermediates that damage photosynthetic machinery. This study shows the potential of using a thermoacidophilic red alga of the order Cyanidiales to model in situ algal gene expression dynamics as a function of UV exposure and seasonal shifts in UV-VIS intensity. These algae exhibit a dynamic seasonal biomass fluctuation referred to as 'mat decline' where viability drastically decreases as seasonal UV-VIS irradiance intensity increases. In Yellowstone National Park (YNP), temporal experiments coupling UV irradiance manipulations (filtering) with whole-community transcription profiling revealed significant cyanidial gene expression changes occurring as a result of exposure to UV, and that patterns of response adjust across low and high irradiance time periods. Separate analyses examined genes responding to either increasing seasonal UV or VIS intensity, or by the combined effects of both irradiance wavelengths (UV and VIS). Results not only corroborated known physiological changes to solar irradiance, but also suggested the strategies employed to deal with excess VIS and UV intensity may be highly integrated. Finally, a suite of comparative analyses determined the relative utility of environmental transcriptomics technologies in studying ecologically-relevant expression patterns. Results suggest in situ expression profiles will improve understanding of how photosynthetic organisms are responding to environmental stressors as they are observed in nature.
Project description:Regulation of gene expression is essential for normal development and cellular growth. Transcriptional events are tightly controlled both spatially and temporally by specific DNA-protein interactions. In this study we finely map the genome-wide targets of the CREB protein across all known and predicted human promoters, and characterize the functional consequences of a subset of these binding events using high-throughput reporter assays. To measure CREB binding, we used HaloCHIP, an antibody-free alternative to the ChIP method that utilizes the HaloTag fusion protein, and also high-throughput promoter-luciferase reporter assays, which provide rapid and quantitative screening of promoters for transcriptional activation or repression in living cells.
Project description:Ultra-violet (UV) and high-intensity visible (VIS) radiation are environmental stressors known to harm photosynthetic organisms through the generation of reactive intermediates that damage photosynthetic machinery. This study shows the potential of using a thermoacidophilic red alga of the order Cyanidiales to model in situ algal gene expression dynamics as a function of UV exposure and seasonal shifts in UV-VIS intensity. These algae exhibit a dynamic seasonal biomass fluctuation referred to as 'mat decline' where viability drastically decreases as seasonal UV-VIS irradiance intensity increases. In Yellowstone National Park (YNP), temporal experiments coupling UV irradiance manipulations (filtering) with whole-community transcription profiling revealed significant cyanidial gene expression changes occurring as a result of exposure to UV, and that patterns of response adjust across low and high irradiance time periods. Separate analyses examined genes responding to either increasing seasonal UV or VIS intensity, or by the combined effects of both irradiance wavelengths (UV and VIS). Results not only corroborated known physiological changes to solar irradiance, but also suggested the strategies employed to deal with excess VIS and UV intensity may be highly integrated. Finally, a suite of comparative analyses determined the relative utility of environmental transcriptomics technologies in studying ecologically-relevant expression patterns. Results suggest in situ expression profiles will improve understanding of how photosynthetic organisms are responding to environmental stressors as they are observed in nature. 16 samples with 3 biological replicates each.
Project description:UV cross-linking and immunoprecipitation (CLIP) and individual-nucleotide resolution CLIP (iCLIP) are the most frequently used methods to study protein-RNA interactions in the intact cells and tissues, but their relative advantages or inherent biases have not been evaluated. To benchmark CLIP and iCLIP method, we performed iCLIP with Nova protein, which is the most extensively studied protein by CLIP. Further, we assessed UV-C-induced cross-linking preferences, by exploiting the UV-independent formation of covalent RNA cross-links of the mutant RNA methylase NSUN2.
Project description:Nonlinear optical imaging modalities, such as stimulated Raman scattering (SRS) microscopy, use pulsed-laser excitation with high peak intensity that can perturb the native state of cells. In this study, we used bulk RNA sequencing, quantitative measurement of cell proliferation, and fluorescent measurement of the generation of reactive oxygen species (ROS) to assess phototoxic effects of near-IR pulsed laser radiation, at different time scales, for laser excitation settings relevant to SRS imaging. We define a range of laser excitation settings for which there was no significant change in mouse Neuro2A cells after laser exposure. This study provides guidance for imaging parameters that minimize photo-induced perturbations in SRS microscopy to ensure accurate interpretation of experiments with time-lapse imaging or with paired measurements of imaging and sequencing on the same cells.
Project description:In this study, we performed integrative multi-omics studies to understand the complex mechanisms underlying UV photobiological effects. While H3K27ac and genetic mutations can both contribute to UV-induced transcriptomic changes, additional omics-based studies on other histone modifications, DNA methylation, and whole genome mapping of genetic mutations will provide a thorough understanding of UV-gene interactions in skin disease pathogenesis. The new UV target genes that we identified have important clinical implications in skin carcinogenesis..
Project description:After DNA damage, cells activate p53, a tumor suppressor gene, and select a cell fate (e.g., DNA repair, cell cycle arrest, or apoptosis). Recently, a p53 oscillatory behavior was observed following DNA damage. However, the relationship between this p53 oscillation and cell-fate selection is unclear. Here, we present a novel model of the DNA damage signaling pathway that includes p53 and whole cell cycle regulation and explore the relationship between p53 oscillation and cell fate selection. The simulation run without DNA damage qualitatively realized experimentally observed data from several cell cycle regulators, indicating that our model was biologically appropriate. Moreover, the comprehensive sensitivity analysis for the proposed model was implemented by changing the values of all kinetic parameters, which revealed that the cell cycle regulation system based on the proposed model has robustness on a fluctuation of reaction rate in each process. Simulations run with four different intensities of DNA damage, i.e. Low-damage, Medium-damage, High-damage, and Excess-damage, realized cell cycle arrest in all cases. Low-damage, Medium-damage, High-damage, and Excess-damage corresponded to the DNA damage caused by 100, 200, 400, and 800 J/m(2) doses of UV-irradiation, respectively, based on expression of p21, which plays a crucial role in cell cycle arrest. In simulations run with High-damage and Excess-damage, the length of the cell cycle arrest was shortened despite the severe DNA damage, and p53 began to oscillate. Cells initiated apoptosis and were killed at 400 and 800 J/m(2) doses of UV-irradiation, corresponding to High-damage and Excess-damage, respectively. Therefore, our model indicated that the oscillatory mode of p53 profoundly affects cell fate selection.