Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To examine the functional relationship between distinct cis-active elements within the distal enhancer region of the rat PRL gene, we have used deletional and mutational analysis of that region in transient transfection studies in GH3 pituitary tumor cells. Results from these studies demonstrate that the region of the PRL distal enhancer containing the Pit-1-binding sites is critical not only for enhancer activity and the response to cAMP, but also for the response to estradiol. An interaction of the estrogen receptor with factors conferring basal enhancer activity is suggested by studies with a mutant distal enhancer region in which the PRL estrogen response element was converted to a palindromic estrogen response element. To directly examine potential interactions, cotransfection studies using PRL distal enhancer reporter gene constructs and expression vectors for Pit-1 and rat estrogen receptor were performed in two heterologous cell lines. The activity of the reporter gene under the control of the PRL distal enhancer linked to either the thymidine kinase promoter or the PRL proximal promoter was not significantly altered by cotransfection with the Pit-1 expression vector in COS-1 or RAT-1 cells. Coexpression of these reporter constructs and an expression vector for estrogen receptor resulted in only a slight response to estradiol. However, when both Pit-1 and estrogen receptor were cotransfected with the distal enhancer reporter gene, a marked induction was observed in response to estradiol, and this activity was dependent upon the concentration of the Pit-1 expression vector.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1990 Dec
PMID:Both Pit-1 and the estrogen receptor are required for estrogen responsiveness of the rat prolactin gene. 208 92

TRH and phorbol dibutyrate (PDBu) stimulate PRL secretion and synthesis from GH4C1 rat pituitary cells through activation of protein kinase C (PKC). TRH responses are mediated by increases in cellular levels of two PKC activators, Ca2+ and diacylglycerol (DAG), whereas PDBu acts as a DAG analog. We conducted experiments to compare the effects of Ca2+ and PDBu/DAG on alpha-PKC redistribution and to determine to what components of the particulate fraction activated alpha-PKC associates. Subcellular fractionation experiments demonstrated that TRH and PDBu both caused chelator-stable association of alpha-PKC with the particulate fraction. In contrast, Ca2+-mediated association with the particulate fraction was not chelator stable. Immunocytofluorescence experiments also demonstrated that TRH, PDBu, and increased cytosolic Ca2+ (due to ionomycin or K+ depolarization) caused redistribution. The effect of TRH was rapid and transient, similar to TRH stimulation of phospholipase C. The translocated alpha-PKC in the particulate fraction from TRH- or PDBu-treated cultures was not solubilized with Triton X-100. In comparable studies using an immunofluorescence assay, alpha-PKC immunofluorescence remained in detergent-insoluble preparations from TRH- and PDBu-stimulated, but not resting cells. The association of activated alpha-PKC with chelator- and detergent-insoluble material suggested that activated alpha-PKC may be associated with membrane and cytoskeletal components.
Mol Endocrinol 1990 Jan
PMID:Activation of alpha-protein kinase C leads to association with detergent-insoluble components of GH4C1 cells. 210 89

To determine whether hormone-dependent changes in the levels of LH/CG receptor in the rat ovary are associated with changes in expression of LH/CG receptor mRNAs, total RNA from rat follicles and corpora lutea at various stages of development was prepared and analyzed by Northern blots and/or solution hybridization. Whereas small antral follicles contained lo amounts of LH/CG receptor mRNAs, the growth of preovulatory (PO) follicles was associated with an increase in all LH/CG receptor mRNA transcripts. Induction of LH/CG receptor mRNAs in granulosa cells of hypophysectomized rats was dependent on the synergistic effects of estradiol and FSH. An LH/CG surge in vivo or LH treatment of PO follicles in vitro caused a rapid decline of all LH/CG receptor mRNAs in PO follicles, which was prevented by cycloheximide. Newly formed corpora lutea (days 1-4 postovulation) contained low amounts of LH/CG receptor mRNAs unless the rats were pregnant or treated exogenously with PRL. During pregnancy, corpora lutea isolated on days 4-19 of gestation contained high levels of LH/CG receptor mRNAs, which decreased markedly on days 21 and 24, the time of functional luteolysis and decreasing LH/CG receptor levels. These studies demonstrate that hormonal regulation of LH/CG receptor mRNA in rat ovarian cells parallels changes in LH/CG receptor levels and involves diverse molecular mechanisms, including 1) low concentrations of cAMP (elicited by FSH) in developing follicles, 2) inhibition by high concentrations of cAMP (elicited by LH/CG) in PO follicles, and 3) induction and maintenance by PRL in corpora lutea of gestation.
Mol Endocrinol 1990 Dec
PMID:Hormonal regulation of luteinizing hormone/chorionic gonadotropin receptor mRNA in rat ovarian cells during follicular development and luteinization. 212 56

Using a recently cloned rat ovary 3 beta-HSD cDNA and antibodies raised against purified human placental 3 beta-HSD, we have studied the effects of treatment with human chorionic gonadotropin (hCG) and hyperprolactinemia achieved by pituitary implants, alone or in combination, on the expression and activity of ovarian 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) in intact adult rats. 32P- and 35S-labeled cDNA probes were used to evaluate the effects of treatments on 3 beta-HSD mRNA levels by dot blot and in situ hybridization, respectively, while enzymatic activity was measured by the conversion of [14C]dehydroepiandrosterone into [14C]androstenedione. The present data show that hCG exerts a marked trophic effect on rat corpora lutea with an increase in total ovarian 3 beta-HSD mRNA levels, 3 beta-HSD protein content as well as enzymatic activity, resulting in an increase in serum progesterone levels. Prolactin-secreting pituitary implants alone, on the other hand, while exerting small effects on 3 beta-HSD expression and activity, led to a marked potentiation of the stimulatory effect of hCG on all parameters. The present data show that hCG and PRL act synergistically to stimulate ovarian progesterone secretion via an increase in 3 beta-HSD mRNA levels, protein content and enzymatic activity.
Mol Cell Endocrinol 1990 Aug 20
PMID:Effects of human chorionic gonadotropin (hCG) and prolactin (PRL) on 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) expression and activity in the rat ovary. 214 42

The biological activities of the GH-PRL family of hormones are mediated by selective binding to two classes of cell membrane receptors, somatogen and lactogen. Primate GH such as human GH (hGH) are unusual in that they bind to both classes of receptors. Replacement of exons 3 or 4 of the hGH gene by the corresponding exons of the rat PRL or rat GH genes results in the synthesis of chimeric proteins which retain the ability to bind to lactogen receptors but can no longer bind to somatogen receptors. This selective loss of somatogen receptor binding in the chimeric proteins suggests that certain of the structural determinants of somatogen and lactogen receptor binding activities in hGH are distinct and can be separately modified by a limited number of amino acid substitutions.
Mol Endocrinol 1990 Jan
PMID:Alteration in the receptor binding specificity of human growth hormone by genomic exon exchange. 215 72

Transcription of the beta-casein milk protein gene in the HC11 mouse mammary epithelial cell line is induced synergistically by the hormones glucocorticoid and PRL. Sequential treatment of HC11 cells with glucocorticoid and PRL demonstrated that the two hormones had different modes of action on beta-casein transcription. Pretreatment with dexamethasone enhanced the response to subsequent induction by PRL, but not vice versa. Dexamethasone increased the sensitivity of the cells to respond to PRL. The increase in sensitivity was slow, extended for 16 days, and could be rapidly reversed by withdrawal of dexamethasone. The dexamethasone-induced sensitivity for the rapid transcriptional regulation by PRL could be observed with transfected rat beta-casein promoter-chloramphenicol acetyltransferase constructs retaining only 175 basepairs upstream from the transcription initiation site. Expression of the endogenous mouse beta-casein gene was regulated identically to that of the promoter constructs with respect to the synergy of the hormones and their different kinetics of action. In contrast to the slow induction of sensitivity toward PRL, dexamethasone rapidly induced the transcription of a mouse mammary tumor virus long terminal repeat controlled gene in HC11. This demonstrated a normal transcriptional activation of the glucocorticoid receptor in this cell line. Thus, glucocorticoid may regulate beta-casein gene transcription indirectly, inducing or repressing other glucocorticoid-regulated genes, whereas the interaction of PRL with its receptor causes a rapid induction of the beta-casein gene promoter.
Mol Endocrinol 1990 Jun
PMID:Prolactin and glucocorticoid hormones control transcription of the beta-casein gene by kinetically distinct mechanisms. 217 95

To identify DNA regions important for basal and hormone-stimulated transcription of the rat PRL gene, a series of clustered point mutations were prepared within the immediate 5' flanking region. DNA fragments representing the wild-type and 19 different linker-scanner mutations of the PRL gene were each linked to a luciferase marker gene, and the DNA constructs were transferred into GH3 pituitary tumor cells by electroporation. Luciferase activity was determined 24 h after transfection in extracts from control cells or cells treated with 0.5 mM chlorophenylthio-cAMP, 100 nM TRH, or 100 nM phorbol myristate acetate. The individual clustered point mutations covered a region from just up-stream of the TATA box (position -30) to a position 193 basepairs up-stream from the start of transcription. Five regions in which mutations produced substantial decreases in both basal and cAMP-, TRH-, or phorbol ester-stimulated expression of the marker gene were detected. Three of these regions (positions -41 to -58, -113 to -124, and -149 to -156) correspond to previously identified binding sites for the pituitary-specific, homeobox protein, Pit-1/GHF-1. The fourth and fifth regions do not correspond to Pit-1/GHF-1-binding sites and presumably represent sites for an unidentified factor. Within these regions, sequences with some similarity to a consensus cAMP response element and an AP-2-binding site have been detected. These data confirm the importance of Pit-1/GHF-1 as a key factor in PRL gene transcription. In addition, the results suggest that additional transcription factors are probably required for efficient expression of the PRL gene.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1990 Oct
PMID:Clustered point mutation analysis of the rat prolactin promoter. 217 21

These studies were designed to further elucidate the relative contributions of transcriptional and posttranscriptional mechanisms involved in beta-casein gene regulation in the mammary epithelial cell line designated COMMA-D and a clonal subline desginated HC-11. Primary transcripts were mapped under various hormonal and substratum conditions using the technique of nuclear run-on transcription and single stranded sense and antisense probes spanning the beta-casein gene. In the presence of insulin alone very little sense transcription is detectable, but antisense transcription is observed, which originates at least 150 basepairs upstream of the normal start site of transcription and is present regardless of hormonal, cell substratum, cell type, or gene activity. Antisense transcription is also detectable in the 3' end of the gene. Insulin, glucocorticoids, and PRL are all necessary for a maximal increase in transcription. A 2- to 4-fold increase in transcriptional activity is observed in the presence of insulin and PRL compared to insulin alone, and this is accompanied by a 125-fold increase in the level of beta-casein mRNA. All three hormones act synergistically to induce a 10-fold increase in transcriptional activity, but the transcriptional increase across the gene is not equimolar. The 5' half of the gene is transcribed at a level that is 2- to 10-fold lower than that of the 3' half of the gene. These studies reveal a significant transcriptional component to beta-casein gene regulation which was not heretofore detected using double stranded cDNA probes representative of only the 3' half of the gene.
Mol Endocrinol 1990 Nov
PMID:Transcriptional analysis of the mouse beta-casein gene. 228 Jul 71

We have previously described a method for producing recombinant methionyl bovine PRL (Met-bPRL), which is as bioactive as the authentic hormone in the Nb2 cell lactogen bioassay; in contrast, a Met-bPRL variant lacking tyrosine 28 was essentially devoid of bioactivity. In the present study we have investigated this loss of bioactivity at the molecular level by determining the bioactivities of a number of Met-bPRL variants engineered to contain specific changes in their primary structures. It was found that the presence of tyrosine per se at the 28 position in Met-bPRL was not essential for high bioactivity, since Met-bPRL variants prepared by replacing tyrosine 28 with other amino acids (arginine, phenylalanine, alanine, and histidine) still had substantial bioactivity (40-74% that of Met-bPRL). Neither was the loss of bioactivity related to a shift in the relative positions of conserved histidines 27 and 30; in fact, histidine 27 was found not to be essential for the bioactivity of the hormone. The loss of bioactivity after deletion of tyrosine 28 from Met-bPRL appears to be related to the removal of an amino acid from the middle of a putative helix (no. 1) rather than to the loss of a residue specific to lactogen function. This suggestion is supported by the finding that Met-bPRL variants obtained by deletion of selected single amino acids from center domains of putative helix 2, 3, or 4 were also essentially devoid of bioactivity. It is speculated that this lack of bioactivity reflects an inability of the proteins to assume a native conformation.
Mol Endocrinol 1990 Jul
PMID:Recombinant methionyl bovine prolactin: loss of bioactivity after single amino acid deletions from putative helical regions. 228 3

PRL storage in GH4C1 cells, rat pituitary tumor cells, can be induced by treatment with a combination of estradiol, epidermal growth factor, and bovine insulin. This increase in storage is characterized by a preferential increase in intracellular PRL compared with secreted PRL and a 50-fold increase in the number of secretory granules. Treatment with the combined hormones stimulates PRL synthesis approximately 6-fold, but this effect is not sufficient to increase PRL storage, because epidermal growth factor alone increases PRL synthesis to the same extent without affecting storage. The cDNA for human proinsulin down-stream of the RSV-LTR promoter was transfected into GH4C1 cells to determine whether storage of another protein known to be targeted to the regulated pathway would also increase with hormone treatment. Proinsulin and PRL release were stimulated over the same time course and to the same peak height, compared to basal release, by both KCl and TRH, indicating that proinsulin is targeted to the regulated pathway in GH4C1 cells. There was little intracellular processing of proinsulin to insulin. Proinsulin synthesis increased 3.9-fold with the combined treatment, assessed by accumulation of proinsulin immunoreactivity in the medium and increases at the mRNA level. Treatment with the combined hormones did not cause the preferential increase in intracellular proinsulin that occurred with PRL; the increase in intracellular proinsulin could be accounted for primarily by effects on synthesis. These results suggest that storage of the two hormones can be differentially regulated.
Mol Endocrinol 1990 Jul
PMID:Prolactin and insulin are targeted to the regulated pathway in GH4C1 cells, but their storage is differentially regulated. 228 4


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>