Protein synthesis inhibitors prevent the induction of laminin B1, collagen IV (alpha 1), and other differentiation-specific mRNAs by retinoic acid in F9 teratocarcinoma cells.

Several differentiation-specific genes, including those for collagen IV and laminin, are induced by retinoic acid (RA) in mouse F9 teratocarcinoma cells. Dibutyryl cAMP can enhance the effect of RA in these cells, but dibutyryl cAMP alone does not induce these genes. Inhibition of RNA synthesis with 5-6-dichloro-1-B-D-ribofuranosylbenzimidazole prevents the induction of these genes by RA; inhibition of DNA synthesis with aphidicolin does not prevent the induction. In vitro transcription studies (Wang et al., Dev. Biol., 107:75-86, 1985) demonstrate that these differentiation-specific genes are regulated by RA at least partially at the level of transcription. To determine whether the regulation of transcription of these differentiation-specific genes is a primary effect of RA, we measured the sensitivity of the induction of mRNAs specific for these RA-inducible genes to inhibitors of protein synthesis. RNA was isolated from F9 cells that had been treated for 20 hr with RA (with or without dibutyryl cAMP) in the presence or absence of either cycloheximide or puromycin. We then hybridized the 32P-labeled recombinant plasmids collagen IV (alpha 1) (pcI5), laminin B1 (pcI56), and pcJ6 to RNA from the treated cells. Both cycloheximide and puromycin inhibited the RA induction of the collagen IV (alpha 1), laminin B1, and J6 mRNAs. In contrast, in a control experiment, a 20-hr treatment with cycloheximide did not inhibit the accumulation of metallothionein I-specific mRNA in response to zinc in F9 cells. Thus protein synthesis is required for the expression of the collagen IV (alpha 1), laminin B1, and J6 genes, and this result suggests that the transcriptional regulation of these genes by RA is indirect.