Expression of rat thyrotropin-releasing hormone (TRH) gene in TRH-producing tissues of transgenic mice requires sequences located in exon 1.
TRH, an amidated tripeptide secreted by certain hypothalamic neurons, is a principal regulator of TSH secretion and thyroid hormone release. TRH is also produced by other neurons in the central nervous system, where it appears to function as a neuromodulator or neurotransmitter, and by certain endocrine cells, where it may act as an autocrine or paracrine factor. The genomic organization of the rat TRH (rTRH) gene is well understood; however, the domains of the rTRH gene that regulate expression are less well characterized. We observed that the region between -47 and +6 of the rTRH gene (relative to the transcription start site at +1) was active in CA-77 cells, a medullary thyroid carcinoma cell line model of TRH production, but was not active in transgenic mice. Inclusion of most of exon 1 (84 out of 103 bp; -47 to +84) increased promoter activity in CA-77 cells and was active in transgenic mice, principally in tissues that normally express the TRH gene. Further lengthening of the 5' end to -243, -547, or -776 retained this expression in TRH-producing tissues in transgenic mice, while further increasing activity in CA-77 cells. These results suggest that cis element(s) located within exon 1 are necessary for the expression of the rTRH gene in vivo.
Balkan
W
W
Veterans Affairs Medical Center, and Department of Medicine, University of Miami School of Medicine, Florida 33125, USA. wbalkan@mednet.med.miami.edu
Tavianini
M A
MA
Gkonos
P J
PJ
Roos
B A
BA
D000818:Animals; D001483:Base Sequence; D005091:Exons; D005786:Gene Expression Regulation; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000096:biosynthesis / Q000235:genetics*; D019076:Transgenes; D014407:Tumor Cells, Cultured
D013973:Thyrotropin-Releasing Hormone