An early effect of retinoic acid: cloning of an mRNA (Era-1) exhibiting rapid and protein synthesis-independent induction during teratocarcinoma stem cell differentiation.
Vitamin A and its derivatives (retinoids) exhibit profound effects on the proliferation and differentiation of many cell types. However, the molecular mechanism by which retinoids exert these effects is unknown. Cultured murine F9 teratocarcinoma stem cells, which differentiate into nontumorigenic endoderm cells in response to retinoic acid (RA), have been used to identify genes regulated by RA. A cDNA library synthesized from F9 cells treated with RA for 8 hr has been screened with a cDNA probe enriched for sequences rapidly induced by RA, and a gene that exhibits the characteristics of a primary target for RA has been identified. This gene, early retinoic acid-1 (Era-1), encodes a 2.2- to 2.4-kilobase polyadenylylated RNA; the level of Era-1 mRNA rapidly and transiently increases up to 35-fold, depending on the concentration of exogenous RA. The increase in Era-1 mRNA is dependent on the continuous presence of exogenous RA. The RA-associated increase in Era-1 mRNA is seen even in the presence of protein synthesis inhibitors, but the increase is prevented by inhibitors of RNA synthesis such as actinomycin D. This increase in the steady-state level of Era-1 mRNA in F9 cells is a very early effect of retinoic acid on gene expression in this differentiation system.