Figure 4. PI3K counter-regulates Jab1 induction of E2F1 apoptotic target genes. (A) Microarray data sets from this study (shJab1) and a previous study looking at Serum/PI3K repression of E2F1 target genes were combined, normalized using distance weighted discrimination (DWD), and subjected to unsupervised hierarchical clustering. Clusters were visualized using Java TreeView. Red shading represents relatively higher gene expression, and green shading corresponds to relatively lower gene expression. Only expression arrays with E2F1 added are included, to better display reductions in gene expression caused by the shJAB1 or Serum/PI3K lanes. (B) PI3K activity blocks Jab1/E2F1 target gene induction. Quiescent REF52 cells were infected with control, E2F1, Jab1 and PI3K expressing adenovirus, mRNA was isolated 24 h post-infection and used for real-time PCR analysis looking at p19^ARF and Cyp26b1 gene induction. Results are reported as fold-inductions compared with gene expression in control (CMV) infected cells.