Transcriptional control of thyroglobulin gene expression by cyclic AMP

Transcription of thyroglobulin (Tg) gene is under the positive control of thyrotropin (TSH). The mechanism of this control has been further investigated. Rats were treated with triiodothyronine (T3) to decrease their endogenous TSH production. Following the intravenous injection of bovine TSH, a 3-fold stimulation of Tg gene transcription could be detected in isolated nuclei as early as 1 h after treatment. The TSH effect was also observed in tissue fragments incubated in vitro under conditions where a concomitant stimulation of cAMP accumulation was detected. Forskolin, a universal activator of adenylate cyclase, was able to mimic TSH action on Tg gene transcription. We conclude that TSH controls transcription of Tg gene directly via its known interaction with receptors on thyrocytes and that cAMP is a physiological mediator of this effect.