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HSF1 regulates transcription of sex-chromosomal multicopy genes during post-meiotic repression

ABSTRACT: Mapping of in vivo targets for HSF1 by using mammalian tissue material in a global ChIP-chip promoter screen. Chromatin was isolated from three wild-type (WT) mouse testes, crosslinked and sonicated into fragments of 100-500 bp, and the quality of the DNA was controlled before the immunoprecipitation, showing no signs of degradation. The DNA amplified from the HSF1 immunoprecipitation samples was labeled and hybridized against the total input DNA samples, on a 1.5 kb promoter tiling array (NimbleGen Systems Inc.), covering ~26000 promoters of the mouse genome. After hybridization and scanning, HSF1 hybridization signals were Lowess normalized to produce log2 ratios (HSF1 ChIP/Input DNA) for all replicate arrays. The promoter values were calculated as average log2 ratios over all probes for each promoter. To identify the HSF1 target population, we used a non-arbitrary analysis method called RankProd described in Breitling et al. 2004. RankProd has been published as an R/Bioconductor package.

ORGANISM(S): Mus musculus

PROVIDER: GSE22492 | GEO | 2010/08/31

SECONDARY ACCESSION(S): PRJNA128685

REPOSITORIES: GEO

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Project description:Samples from 20 children with B-cell precursor ALL, comprising ten with high hyperdiploidy and ten with the ETV6/RUNX1 fusion, were included in the study. Four Âµg of methylated and input fraction DNA were analyzed with a classic MeDIP assay and subsequent microarray hybridization using the NimbleGen CpG Island-Plus-Promoter Array (Roche NimbleGen, Madison, WI).<br><br>This array platform covers all 28,226 UCSC-annotated CpG islands and promoter regions for all RefSeq genes, including 385,000 probes of 50-75mer length per array, with an upstream and downstream promoter tiling of 800 bp and 200 bp, respectively. Signal intensity data were extracted from the scanned images. Each feature on the array has a corresponding log2 ratio, which is the ratio of the input signals for the methylated DNA and the input fraction DNA. The log2 ratio was scaled in order to center the ratio data around zero by subtracting the bi-weight mean for the log2 ratio values for all features on the array from each log2 ratio value. A modified ACME algorithm, where a fixed-length window (750 bp) is placed around each consecutive probe, and the one-sided Kolmogorov-Smirnov test were then applied on the scaled log2 ratio data to determine whether the probes were drawn from a significantly more positive distribution (peak) of intensity log2 ratios than the other probes in the array. The resulting score for each probe is the -log10 p-value from the windowed Kolmogorov-Smirnov test around that probe. Peak data were generated by searching for probes above a p-value minimum cut-off (-log10) of 2.<br><br>Peaks within 500 bp of each other were merged. Each annotated gene was subsequently searched for peaks appearing in a specified promoter region around the transcription start site. The region searched was design-specific, spanning from 5 kb upstream to 1 kb downstream of the transcription start site. Genes that had at least two probes with peaks above the p-value minimum cut-off were considered to have significant CpG island methylation scores for hypermethylation.

Project description:Limb buds were dissected from E10.75 mouse embryos, fixed in 1% formaldehyde for 15 min at room temperature, washed 3 times with cold PBS and stored at -800C. Pools of 16 limb buds were used for each ChIP-chip experiment. ChIP was performed according to (Lee et al., 2006) using 2 ?g of anti-CTCF antibodies (A300-543A, Bethyl Laboratories) and EZview Red Protein G/A Affinity Gel (Sigma). Immunoprecipitated and whole cell extract DNA (input) were treated with RNaseA, proteinase K and purified by 2 rounds of extraction with phenol:chloroform: isoamyl alcohol. ChIP and input DNA were amplified using Ligation-Mediated PCR (Lee et al., 2006). PCR was limited to 15 cycles. 1.5 ?g of ChIP and input DNA were fragmented and labeled using GeneChip WT Double-Stranded DNA Terminal Labeling Kit (Affymetrix) and hybridized to the Chromosome 2 and X tiling arrays (Affymetrix). Tiling arrays data were quantile normalized within cDNA/genomic DNA or ChIP/ input replicate groups using R packages, STARR and Ringo (Zacher et al., 2010; Toedling et al., 2007). The ratio of probe intensity between the experiment and the control groups were computed considering the median values over replicates. The ratios were smoothened by computing the running medians with a half window size set to 150 bp and a minimum of 5 probes per window. To identify enriched regions a minimum of 3 consecutive probes with a smoothed ratio exceeding a threshold have been considered. The threshold has been fixed by taking the 99th percentile of the estimated null distribution of the ratios. Only ChIP enriched regions with score log2?1.5 and width ?150 bp were considered for further analysis. As a complement, array data were quantile normalized within ChIP/input replicate groups and scaled to medial feature intensity of 500 using TAS software (Affymetrix). For each genomic position, a dataset was generated consisting of all probes mapping within a sliding window of 250 bp. The averaged ratios were plotted along the genomic DNA sequence using Integrated Genome Browser (IGB) software (Affymetrix).

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HSF1 regulates transcription of sex-chromosomal multicopy genes during post-meiotic repression

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