Experimental setup. U937 cells were differentiated with 10 nM TPA for 48 h or left untreated. Then, cells were trypsinized, washed with PBS, and reseeded in fresh medium. After 24 h, the conditioned medium from activated U937 monocyte-derived macrophages (CM) or undifferentiated U937 monocytes (Ctr) was harvested. MCF7 cells were incubated for 4 h with CM or Ctr. Subsequently, the respective cellular lysates were subjected to polysomal fractionation. Equal aliquots of RNA isolated from single fractions were analyzed using denaturing agarose gel electrophoresis to verify 28S and 18S rRNA distribution as indicators for ribosome distribution. Pooled polysomal fractions 6–10 and total RNA were analyzed using whole genome microarrays. Comparing polysomal changes (CM vs. Ctr) with total changes (CM vs. Ctr) revealed translationally regulated genes.
