Stabilization of the mRNA for the uncoupling protein thermogenin by transcriptional/translational blockade and by noradrenaline in brown adipocytes differentiated in culture: a degradation factor induced by cessation of stimulation?

The stability of the mRNA coding for the uncoupling protein thermogenin was investigated in mouse brown-fat cells differentiated in culture. After 7 days in culture, the cells were stimulated for 24 h with noradrenaline, and a high level of thermogenin mRNA was then observed. If noradrenaline treatment was continued, the mRNA level remained high, but, upon withdrawal of noradrenaline, the level decreased rapidly, with a half-life of only 2.7 h. The presence of transcriptional (actinomycin) or translational (cycloheximide) inhibitors prolonged the apparent half-life by about 50%. The presence of noradrenaline during transcriptional blockade led to a further stabilization of thermogenin mRNA. It was concluded that an induced (or short-lived) gene product is important for thermogenin mRNA degradation. Direct interaction of noradrenaline with the cultured brown adipocytes could apparently not mimic the paradoxical destabilization of thermogenin mRNA in vivo, previously observed in the cold-exposed mouse [Jacobsson, Cannon and Nedergaard (1987) FEBS Lett. 244, 353-356], indicating significant differences between the systems in vitro and in vivo.