Project description:During mitosis, RNA polymerase and most transcription factors are excluded from the chromosomes and transcription ceases. The transcriptional re-activation of the genome, following mitosis, requires the re-setting of cell-type specific programs that were initially established during development. However, only about one-fifth of transcription factors are retained on chromosomes throughout mitosis and a subset of these have been shown to facilitate target gene reactivation during mitotic exit. How such “bookmarking” factors bind to chromatin in mitosis and re-activate transcription is central to the stability of transcriptional programs across multiple cell cycles. We compared a diverse set of transcription factors involved in liver differentiation and found different modes of mitotic chromosome binding. The pioneer transcription factor FoxA1, which is among the first to bind liver genes in development, exhibits virtually complete mitotic chromosome binding, whereas other liver factors bind with a range of efficiencies. Yet genome-wide analysis shows that only about 15% of the FoxA1 interphase target sites are bound in mitosis; the latter include sites at genes for maintaining cell differentiation. FoxA1 mutants that perturb specific and nonspecific DNA binding reveal a significant contribution of nonspecific binding events in mitotic chromatin. Such nonspecific binding appears to spread from interphase FoxA1 targets and may serve as storage sites. The hierarchy of specific binding, nonspecific binding, partial chromatin binding, and failure to bind mitotic chromosomes reflects the temporal sequence of the factors’ developmental roles in gene activation. Gene expression was assessed in asynchronously cycling cells in order to determine whether FoxA1 is disposed to bind to high- or low-expressed genes during mitosis. Heatmap analysis shows that FoxA1's mitotic targets are among the highest-expressed genes in asynchronous cells. Total RNA was collected from three different plates with asynchronous HUH7 cells using the RNeasy mini kit (Qiagen Valencia CA). Expression microarrays were performed with a Human Gene 1.OST array (Affymetrix) at the UPenn Microarray Core Facility and assessed using Partek.

Project description:To identify low abundance autocrine growth factors in CHO cell conditioned media, we utilized a label-free shotgun proteomics approach. CHO cell conditioned media were harvested from fed batch bioreactors and concentrated using methanol/chlorofrom precipitation. Proteins in the samples were then subjected to proteolysis with trypsin, and then subjected to primary fractionation using a SCX column, followed by RP liquid chromatography MS (LC-MS) with a LTQ Orbitrap Velos instrument using the data dependent acquisition (DDA) method. The MS system was set up and run with a method which enabled fast acquisitions of high quality peptide precursor and fragment ion data, with the desired precursor mass accuracy of ±5 ppm. For the LTQ Orbitrap Velos MS, the data-dependent MS/MS analytical workflow in positive ion mode was used. Each precursor survey scan (m/z: 300 to 1800) by the Orbitrap mass analyzer (resolution = 60,000 FWHM) was linked to 10 MS/MS events using the 2D ion trap CID approach, with dynamic ion exclusion set at 60 s. This value was determined based on the observed mean peptide chromatographic peak width. All other instrument parameters were set up according to the manufacturer’s suggested values for complex peptide samples. The nano-ESI source was fitted with a 30-µm stainless steel nano-bore emitter (Thermo Fisher Scientific) with 1.7 kV applied near the tip. Raw data files from the LTQ Orbitrap Velos MS were processed using the Proteome Discoverer 1.3 software (Thermo Fisher Scientific). The LC-MS data were searched against the human (Homo sapiens; UniProtKb, updated in August 2012, 45 848 entries), mouse (Mus musculus; UniProtKb, updated in August 2012, 31 528 entries) and chinese hamster (Cricetulus griceus; UniprotKb, updated in August 2012, 24 609 entries) protein databases using the Sequest search engine for the LTQ Orbitrap Velos LC-MS data, assuming tryptic digestion with precursor ions to fall within 10 ppm of projected m/z values and a fragment ion mass tolerance of 0.5 m/z. The specified search parameters were carbamidomethylation of cysteine as fixed modification, oxidation of methionine as dynamic modification and a maximum of two missed cleavage events. Reverse database searching resulted in a specific false discovery rate (FDR) of 1% at the peptide and protein level.

Project description:OBJECTIVE: To determine whether macrophages, a type of cell implicated in the pathogenesis of ankylosing spondylitis (AS), exhibit a characteristic gene expression pattern. METHODS: Macrophages were derived from the peripheral blood of 8 AS patients (median disease duration 13 years [range <1-43 years]) and 9 healthy control subjects over 7 days with the use of granulocyte-macrophage colony-stimulating factor. Cells were stimulated for 24 hours with interferon-gamma (IFNgamma; 100 units/ml), were left untreated for 24 hours, or were treated for 3 hours with lipopolysaccharide (LPS; 10 ng/ml). RNA was isolated and examined by microarray and real-time quantitative reverse transcription-polymerase chain reaction analysis. RESULTS: Microarray analysis revealed 198 probe sets detecting the differential expression of 141 unique genes in untreated macrophages from AS patients compared with healthy controls. Clustering and principal components analysis clearly distinguished AS patients and controls. Of the differentially expressed genes, 78 (55%) were IFN-regulated, and their relative expression indicated a reverse IFN signature in AS patient macrophages, where IFNgamma-up-regulated genes were underexpressed and down-regulated genes were overexpressed. Treatment of macrophages with exogenous IFNgamma normalized the expression of these genes between patients and controls. In addition, the messenger RNA encoded by the IFNgamma gene was approximately 2-fold lower in AS patient macrophages at baseline (P = 0.004) and was poorly responsive to LPS (P = 0.018), as compared with healthy controls. CONCLUSIONS: Our findings reveal consistent differences in gene expression in macrophages from AS patients, with evidence of a striking reverse IFN signature. Together with poor expression and responsiveness of the IFNgamma gene, these results suggest that there may be a relative defect in IFNgamma gene regulation, with autocrine consequences and implications for disease pathogenesis. Experiment Overall Design: Macrophages were derived from the peripheral blood of 8 AS patients (median disease duration 13 years [range <1â??43 years]) and 9 healthy control subjects over 7 days with the use of granulocyteâ?? macrophage colony-stimulating factor. Cells were stimulated for 24 hours with interferon- (IFN; 100 units/ ml), were left untreated for 24 hours, or were treated for 3 hours with lipopolysaccharide (LPS; 10 ng/ml). RNA was isolated and examined by microarray and real-time quantitative reverse transcriptionâ??polymerase chain reaction analysis.

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Expression and FoxA1 binding in asynchronous and mitotic HUH7 cells

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