Evidence for a single rat thyrotropin-beta-subunit gene: thyroidectomy increases its mRNA.

We have isolated and characterized cDNAs representing the rat thyrotropin-beta-subunit. The cDNAs were prepared from poly(A)+ RNA obtained from rat pituitary glands and encode the precursor of the rat thyrotropin-beta-subunit which contains a leader or signal peptide of 20 amino acids, and an apoprotein of 118 amino acids. Blot hybridization analysis of total rat liver DNA digested with several restriction enzymes indicates the likelihood of a single gene encoding the rat thyrotropin-beta-subunit. In addition, analyses of pituitary RNA from normal and thyroidectomized rats indicate that the mRNA encoding the rat thyrotropin-beta-subunit is approximately 700 bases in length and its level increases 8--10-fold after thyroid gland ablation.