Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression

The objectives of this research were to characterize insulin-like growth factor-I (IGF-I) gene expression in cattle, to determine how IGF-I gene expression is affected by nutritional intake and growth hormone (GH) in cattle, and to identify the regulatory DNA region that mediates GH stimulation of I...

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Main Author: Wang, Ying
Other Authors: Animal and Poultry Sciences
Format: Others
Published: Virginia Tech 2014
Subjects:
Online Access:http://hdl.handle.net/10919/30208
http://scholar.lib.vt.edu/theses/available/etd-12212005-194254/
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spelling ndltd-VTETD-oai-vtechworks.lib.vt.edu-10919-302082020-09-26T05:31:39Z Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression Wang, Ying Animal and Poultry Sciences Jiang, Honglin Wong, Eric A. Smith, Edward J. Webb, Kenneth E. Jr. Akers, Robert Michael Signal transducer and activator of transcription 5 Nutrition Transcriptional regulation Insulin-like growth factor-I Growth hormone The objectives of this research were to characterize insulin-like growth factor-I (IGF-I) gene expression in cattle, to determine how IGF-I gene expression is affected by nutritional intake and growth hormone (GH) in cattle, and to identify the regulatory DNA region that mediates GH stimulation of IGF-I gene expression. It was found that transcription of the IGF-I gene in cattle was initiated from both exon 1 and exon 2, generating class 1 and class 2 IGF-I mRNA, respectively. Both classes of IGF-I mRNA appeared to be ubiquitously expressed, with the highest level in liver and with class 1 being more abundant than class 2 in all tissues examined. Class 1 IGF-I mRNA may be also translated more efficiently than class 2 IGF-I mRNA. Liver expression of IGF-I mRNA was decreased (P < 0.01) by food deprivation in cattle, and this decrease was due to an equivalent decrease in both classes of IGF-I mRNA. Liver expression of IGF-I mRNA was increased (P < 0.01) by GH, and this increase resulted mainly from increased expression of class 2 IGF-I mRNA. Using cotransfection analyses, a ~700 bp chromosomal region ~75 kb 5' from the first exon of the human IGF-I gene was found to enhance reporter gene expression in the presence of constitutively active signal transducer and activator of transcription 5 (STAT5) proteins, transcription factors that are known to be essential for GH-increased IGF-I gene expression. This 700 bp DNA region contains two STAT5-binding sites that appear to be conserved in mammals including cattle. Electrophoretic mobility shift assays and cotransfection analyses confirmed their ability to bind to STAT5 proteins and to mediate STAT5 activation of gene expression, respectively. Chromatin immunoprecipitation assays indicated that overexpressed constitutively active STAT5b protein bound to the chromosomal region containing these two STAT5-binding sites in Hep G2 cells, and this binding was associated with increased expression of IGF-I mRNA. These two STAT5-binding sites were also able to mediate GH-induced STAT5 activation of gene expression in reconstituted GH-responsive cells. These results together suggest that the distal DNA region that contains two STAT5-binding sites may mediate GH-induced STAT5 activation of IGF-I gene transcription in vivo. Ph. D. 2014-03-14T20:21:01Z 2014-03-14T20:21:01Z 2005-12-08 2005-12-21 2007-12-30 2005-12-30 Dissertation etd-12212005-194254 http://hdl.handle.net/10919/30208 http://scholar.lib.vt.edu/theses/available/etd-12212005-194254/ dissertation.pdf In Copyright http://rightsstatements.org/vocab/InC/1.0/ application/pdf Virginia Tech
collection NDLTD
format Others
sources NDLTD
topic Signal transducer and activator of transcription 5
Nutrition
Transcriptional regulation
Insulin-like growth factor-I
Growth hormone
spellingShingle Signal transducer and activator of transcription 5
Nutrition
Transcriptional regulation
Insulin-like growth factor-I
Growth hormone
Wang, Ying
Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression
description The objectives of this research were to characterize insulin-like growth factor-I (IGF-I) gene expression in cattle, to determine how IGF-I gene expression is affected by nutritional intake and growth hormone (GH) in cattle, and to identify the regulatory DNA region that mediates GH stimulation of IGF-I gene expression. It was found that transcription of the IGF-I gene in cattle was initiated from both exon 1 and exon 2, generating class 1 and class 2 IGF-I mRNA, respectively. Both classes of IGF-I mRNA appeared to be ubiquitously expressed, with the highest level in liver and with class 1 being more abundant than class 2 in all tissues examined. Class 1 IGF-I mRNA may be also translated more efficiently than class 2 IGF-I mRNA. Liver expression of IGF-I mRNA was decreased (P < 0.01) by food deprivation in cattle, and this decrease was due to an equivalent decrease in both classes of IGF-I mRNA. Liver expression of IGF-I mRNA was increased (P < 0.01) by GH, and this increase resulted mainly from increased expression of class 2 IGF-I mRNA. Using cotransfection analyses, a ~700 bp chromosomal region ~75 kb 5' from the first exon of the human IGF-I gene was found to enhance reporter gene expression in the presence of constitutively active signal transducer and activator of transcription 5 (STAT5) proteins, transcription factors that are known to be essential for GH-increased IGF-I gene expression. This 700 bp DNA region contains two STAT5-binding sites that appear to be conserved in mammals including cattle. Electrophoretic mobility shift assays and cotransfection analyses confirmed their ability to bind to STAT5 proteins and to mediate STAT5 activation of gene expression, respectively. Chromatin immunoprecipitation assays indicated that overexpressed constitutively active STAT5b protein bound to the chromosomal region containing these two STAT5-binding sites in Hep G2 cells, and this binding was associated with increased expression of IGF-I mRNA. These two STAT5-binding sites were also able to mediate GH-induced STAT5 activation of gene expression in reconstituted GH-responsive cells. These results together suggest that the distal DNA region that contains two STAT5-binding sites may mediate GH-induced STAT5 activation of IGF-I gene transcription in vivo. === Ph. D.
author2 Animal and Poultry Sciences
author_facet Animal and Poultry Sciences
Wang, Ying
author Wang, Ying
author_sort Wang, Ying
title Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression
title_short Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression
title_full Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression
title_fullStr Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression
title_full_unstemmed Growth Hormone and Nutritional Regulation of Insulin-Like Growth Factor-I Gene Expression
title_sort growth hormone and nutritional regulation of insulin-like growth factor-i gene expression
publisher Virginia Tech
publishDate 2014
url http://hdl.handle.net/10919/30208
http://scholar.lib.vt.edu/theses/available/etd-12212005-194254/
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