Thyrotropin releasing hormone

Mc, Gershengorn

doi:10.1007/bf00230085

Cited by 83 publications

(20 citation statements)

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“…The prolactin gene is expressed primarily in mammalian pituitary lactotrophs and is regulated by inhibitory and stimulatory hormones from the brain and gonads (6) plus several other classes of factors including Ca2+ (12), phorbol esters (22), and cyclic AMP (16). Previous studies have suggested that most of these factors modulate prolactin production at the level of gene transcription (2,15,16,19,21).…”

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Reconstitution of cell-type-specific transcription of the rat prolactin gene in vitro.

Cao¹,

Barron²,

Carillo³

et al. 1987

Mol. Cell. Biol.

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We present evidence for the existence of prolactin upstream factor I (PUF-I) in rat pituitary-derived cells and demonstrate its interaction with a symmetrical DNA element located in the 5' flanking region of the gene. An in vitro expression system developed from pituitary-derived Gil3 cells was used to determine that 420 base pairs (bp) of 5' flanking DNA was sufficient for cell-specific, accurate, and efficient RNA polymerase II transcription of the rat prolactin gene. Reconstitution of in vitro transcription with pituitary and nonpituitary nuclear extracts suggested that the presence of GH3 cell-specific factors mediated the activation of prolactin gene expression. We also demonstrated that a functionally stable transcription complex assembled on the prolactin promoter. Using DNase I protection procedures, we have identified the DNA-protein binding area in the prolactin 5' flanking region. Gil3 nuclear extracts contain a cell-specific protein (PUF-I) that binds to a 28.bp region (-63 to -36) which contains an 18-bp imperfect palindrome (-63 to -46). The role that the interaction between PUF-I and the imperfect palindrome plays in in vitro pituitary-specific prolactin gene expression is discussed.The prolactin gene is expressed primarily in mammalian pituitary lactotrophs and is regulated by inhibitory and stimulatory hormones from the brain and gonads (6) plus several other classes of factors including Ca2+ (12), phorbol esters (22), and cyclic AMP (16). Previous studies have suggested that most of these factors modulate prolactin production at the level of gene transcription (2,15,16,19,21). Regulation of gene activity is presumably mediated by the interaction of cis-acting promoter elements with transacting nuclear protein transcription factors (8). The 5' flanking prolactin DNA contains homologous sequences for several eucaryotic cis control elements including two TATA boxes at positions -28 to -23 and -142 to -136 and a CAAAT sequence from -192 to -187. In addition, there is an interesting A+T-rich 18-base-pair (bp) imperfect symmetrical sequence from -63 to -46 (4, 17).An investigation of the prolactin cis-acting elements by Nelson et al. (20), using gene transfer methods, suggested the presence of two discrete, separable sequences which act in a position and orientation independent manner to enhance prolactin gene transcription. It was proposed that these two regions (from -1768 to -1712 and from -1653 to -1531) are cell-specific enhancer elements which mediate the activation of these genes in lactotrophs and somatotrophs.We have used a different approach to study the interaction of cis-acting DNA sequences and trans-acting elements leading to an activated rat prolactin gene. Cell-free nuclear extracts prepared from a rat pituitary-derived cell line, GH3, and nonpituitary cells were used to study the cell-specific in vitro transcription and DNA protein-binding interactions of the prolactin gene. We combined transcriptional and binding assays to identify DNA sequences upstream from the prolactin gene whic...

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confidence: 99%

Reconstitution of cell-type-specific transcription of the rat prolactin gene in vitro.

Cao¹,

Barron²,

Carillo³

et al. 1987

Mol. Cell. Biol.

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“…The prolactin gene is capable of responding to a wide variety of extracellular substances (4, 10,17,18,20,23,24). Therefore, it is exciting that the PUF-I-binding region was also recently reported to mediate the transcription-activating effect of epidermal growth factor and phorbol esters (7).…”

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confidence: 99%

Prolactin upstream factor I mediates cell-specific transcription.

1988

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DNA sequence-specific chromatography was used to purify prolactin upstream factor I (PUF-I) approximately 10,000- to 20,000-fold from rat GH3 cells. The purified transcription factor reconstituted enhanced pituitary-specific prolactin RNA synthesis in nonpituitary in vitro transcription assays. In vitro mutagenesis demonstrated that the capacity to stimulate prolactin gene transcription was directly correlated with PUF-I binding to an A+T-rich region located from -63 to -36 in the prolactin 5'-flanking DNA. We propose that PUF-I is a critical modulator of transcriptional activity in pituitary cells and has a central role in the stimulation of prolactin gene transcription in the mammalian pituitary lactotroph.

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“…Treatment of intact cells with TRH causes changes in the pattern of protein phosphorylation that are clearly different from those observed when GH cells are exposed to hormones and drugs known to increase cyclic AMP (12,13). Under different experimental conditions TRH either has no effect upon (6,14) or increases (15) adenylate cyclase activity of pituitary cell membranes. Gautvik et al (15) recently reported that TRH can stimulate GH-cell adenylate cyclase; however, they found that stimulation required higher concentrations of TRH and related peptides than receptor bindThe publication costs of this article were defrayed in part by page charge payment.…”

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confidence: 98%

“…TRH initiates its actions on GH cells by binding to specific membrane receptors, which have been extensively characterized with both intact cells and isolated membranes (3)(4)(5). When intact cells are exposed to TRH, there is a rapid increase in the rate of metabolism of phosphoinositides (6,7) and an increase in cytosolic free calcium ion concentration (8,9). These effects result from receptor occupancy and are thought to be important in generating the biological response in these cells, stimulation of prolactin release and synthesis.…”

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confidence: 99%