Institut de Recherche Interdisciplinaire en Biologie Humaine et Nucléaire, Université Libre de Bruxelles, Belgium.
Two regions hypersensitive to DNase I digestion were found in a 7-kb segment of thyroglobulin gene 5'-flanking sequences in the chromatin from bovine thyroid. The most upstream site (-2000 to -1600 bp relative to the transcriptional start) was found in thyroid chromatin only, but independently of actual expression of the gene. It therefore represents a tissue-specific characteristic which may be associated with the commitment of the thyroglobulin gene to transcriptional activity. The very 5' end of the gene and the proximal promoter sequences (-100 to +60 bp relative to transcriptional start), constitute the second site, the hypersensitive character of which could be directly correlated with transcriptional activity. The structural changes occurring in this region of the chromatin were dependent on cAMP stimulation of the thyroid cells.