These investigations should enhance our understanding of the structure, organization, and regulation of thyrotropin (TSH) genes in mouse and man. This laboratory has already cloned cDNAs to mouse alpha and beta TSH mRNAs extracted from a TSH-secreting pituitary tumor and determined their nucleotide sequences. The cloning of human TSH cDNAs using post-mortem human pituitary glands as the source of mRNA is ongoing. A study of the structure and chromosomal location of TSH genes in mouse and man has been completed using genomic libraries for selection of TSH genes and somatic cell hybrids of known chromosomal content for assignment of TSH genes to specify chromosomes. Chromatin structure of TSH genes, as reflected by DNase sensitivity and methylation, will be evaluated during the evolution of mouse TSH-secreting pituitary tumors. The regions of the 5'-flanking sequences of the alpha and beta TSH genes important for transcription will be determined by the in vitro transcription of specific gene deletion mutants in a HeLa cell extract system. The effects on TSH gene expression of thyroid hormone, glucocorticoids, bromergocryptine, estrogen, and thyrotropin-releasing hormone (TRH) have been investigated. Alpha and beta TSH genes are affected discordantly by thyroid hormone. The molecular level of regulation is being studied: transcription, mRNA processing, pretranslational effects, translational efficiency, and posttranslational effects. TSH genes will be transferred into recipient cells to study their expression and regulation. These basic studies will be performed in conjunction with ongoing clinical studies of patients with pituitary resistance to thyroid hormones and the regulation of their inappropriate TSH secretion, particularly by the dopamine agonist bromergocryptine. These investigations should add considerably to our knowledge of the regulation of TSH gene expression and the mechanism of action of thyroid hormones. (C)
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