Figure 2.

Translation state of human genes monitored on cDNA arrays. Comparison of DNA arrays hybridized with complex ³²P-labeled cDNA probes from the under-translated (Left) and translated (Right) RNA pools of both resting (Lower) and serum-activated human foreskin fibroblasts (Upper). Growth-arrested human foreskin fibroblasts were stimulated to enter the cell cycle by addition of serum and fractionated by centrifugation through a 0.5–1.5 M sucrose gradient (9). The RNA fractions containing one ribosome or less per mRNA were pooled as the under-translated fraction, and fractions loaded with two or more ribosomes per mRNA were pooled as translated fractions (Fig. 1). An equal percentage of the RNA in each fraction was used to prepare complex ³²P-labeled first-strand cDNA probes as recommended by CLONTECH. CLONTECH Altas human cancer cDNA Expression Array filters were hybridized with the ³²P-labeled cDNA probes. The arrows indicate the translationally regulated genes found in this study; 1, vimentin; 2, Stat1; and 3, 23-kDa highly basic protein.