Human HCT116 cell line and an EP300 knock-out HCT116 line (KO) were grown in McCoy's medium containing 10% fetal calf serum. The experiment was done to compare the expression differences between the parent HCT116 cell line and the derived KO cell line. Cells were plated in T75 flasks. They were cultured until they were 80% confluent and harvested by trypsinization followed by pelleting of the cells. All RNA isolation was accomplished with the Tri-Reagent (SIgma) and purified using the Qiagen RNeasy Mini Kit reagents. The RNA (10 ug) was annealed with a random hexamer primer, and reverse-transcribed into cDNA with Powerscript (Clontech) reverse transcriptase for 2h at 42 degrees in the presence of amino-allyl dUTP. The cDNA from KO RNA and HCT116 RNA was covalently coupled separately with Cy3 and Cy5 monoreactive fluors, respectively, in 50 mM sodium bicarbonate, pH 9.0. The Cy3 and Cy5 labelled cDNAs were combined and purified with a QIAquick PCR purification kit and hybridized to the microarray using the Hybrite chamber (Vysis). Fluorescent array images were collected for both Cy3 and Cy5 with a ScanArray 4000 (Perkin Elmer) at a resolution of 10 um at maximum laser power and photo-multiplier tube voltage of 50 to 60%. Segmentation was performed using the histogram method of the QuantArray (Perkin Elmer) package. Data was transformed into log base 2 expression ratios and normalized using scaled loess normalization. Keywords = HCT116, KO, EP300
