[Control of growth hormone synthesis, paradigm of tissue specificity and of hormonal gene expression regulation].

The study of the transcriptional control of the growth hormone gene illustrates the complementary role of three types of regulatory proteins. These proteins bind to the gene upstream of the transcription initiation site to stimulate or inhibit transcription. A first type of proteins includes ubiquitous factors. A second type includes receptors for hormones that act in the nucleus. A third type is represented by the pituitary factor Pit-1, the prototype of a novel class of proteins that are also involved in controlling embryonic development and cell proliferation. Indeed, Pit-1 determines not only the tissue specificity of expression of the growth hormone gene, but also its control by somatocrinin, as well as the ontogeny of the anterior pituitary and the maintenance of the differentiated phenotype.