Studies on regulation of the human gene for insulin-like growth factorbinding protein-1 /
Insulin, glucocorticoids and glucagon (cAMP) interact to
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965911&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Insulin, glucocorticoids and glucagon (cAMP) interact to regulate transcription of many hepatic genes, and this regulation is often crucial to the survival of the indi vidual. The studies presented here begin to investigate the multihormonal regulation of the human gene for insulin-like growth factor binding protein-1 (IGFBP-1) , a protein which helps to regulate serum glucose levels. Basal IGFBP-1 expression in HEP G2 he-catoma cells depends on a proximal promoter element that binds hepatic nuclear factor I (.HNFl) . Cotransfection of HEP G2 and HeLa cells with IGFBP-1 promoter constructs and HNF1 expression vectors indicated that only an HNF1 form containing the -Lransacti-vation domain could stimulate IGFBP-1 promoter activity. This suggests that HNFI is required for basal IGFBP-1 transcription. IGFBP-1 transcription rises with glucocorticoids and cAMP, and falls with insulin. Recent studies suggest -that these hormones regulate transcription by working through DNA elements located in the -oroximal IGFBP-1 -oromoter. Constructs containing IGFBP-1 T)romoter mutations were used in transfection and DNase I protection assays to show a) much of the cAMP response is mediated by the region between -269 and -246 base pairs (bp) 5 to the transcription start site, which has a sequence similar to known cAMP response elements (CREs); and b) binding of CPEB, a protein known to confer CAMP effects,, to mutations of this region correlated with response of these mutations to CAMP. These data suggest that this region is a CRE confering CAMP responsiveness to the IGFBP-1 promoter. IGFBP-1 promoter mutations were also used to identify an element between -140 and -103 bp which confered the inhibitory effect of insulin. Gel mobility-shift assays show that high mobility group proteins I/Y, IRE binding protein, HNF-3(x and HNF-38, were all able to bind specifically to this IGFBP1 IRE. Similarly, promoter mutations and DNase I protection assays identified two glucocorticoid response elements (GREs), located within the first 200 bp of the IGFBP-1 promoter, which act cooperatively to confer glucocorticoids effects. Additional studies found that the IRE identified above a) confers the entire inhibitory effect of insulin on both basal and glucocorticoid-stimulated activity of the IGFBP-1 promoter; and b) this IRE is essential for maximal glucocorticoid- stimulated activity. |
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| Item Description: | Vita. "Major Subject: Veterinary Microbiology". In title, numerals are used. |
| Physical Description: | ix, 98 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |