Genomic Analysis of Glucocorticoid-regulated Promoters in Murine T-lymphoma Cells

We have undertaken a high-throughput analysis to identify targets of glucocorticoid regulation in P1798 murine T-lymphoma cells. G1/S-arrested cultures were treated for 8 hours with 0.1 μM dexamethasone (dex) in the presence and absence of 1 μg/ml cycloheximide. Untreated cultures and cultures exposed to cycloheximide alone were prepared as controls. RNA was isolated and gene expression analyzed using Affymetrix MG-U74A oligonucleotide arrays (Gene Chips®). Three independent experiments were performed. The data were analyzed using a variety of statistical and analytical approaches in order to identify primary transcriptional targets of the glucocorticoid receptor. We identified 44 genes that increase by > 2-fold in both dex-treated and dex + cycloheximide-treated cultures (relative to control and cycloheximide-treated cultures) in three replicate experiments. Statistical analysis of control data indicate that the probability that a given probeset would, as a result of random error, increase > 2-fold both in the presence and absence of cycloheximide in two independent experiments is approximately 7 × 10^-9. We have retrieved from the Celera mouse genomic sequence 8 kb of promoter sequence, spanning 4 kb either side of the 5′-end of the cDNA from eight of the induced genes. These sequences were analyzed for potential glucocorticoid receptor binding sites. Five of these genes contain the sequence ACAnnnTGTnCT within 4 kb of the presumptive transcriptional start site. Eight control genes were selected at random and analyzed for the sequence ACAnnnTGTnCT. Two control genes had such sequences within 4 kb of the transcriptional start site.