TY - JOUR
T1 - Rapid activation of rat insulin-like growth factor-I gene transcription by growth hormone reveals no alterations in deoxyribonucleic acid-protein interactions within the major promoter
AU - Thomas, Michael J.
AU - Kikuchi, Kiyoshi
AU - Bichell, David P.
AU - Rotwein, Peter
PY - 1994/10
Y1 - 1994/10
N2 - Insulin-like growth factor-I (IGF-I) is an important mediator of prenatal and postnatal growth, but little is known about the control of IGF-I gene expression. Previously, we demonstrated that GH rapidly stimulates hepatic IGF-I transcription in vivo in hypophysectomized (hypox) rats. In this study, we show that GH induces IGF-I gene transcription through the major promoter, promoter 1, and identify and characterize DNA-protein interactions throughout the promoter. In vitro deoxyribonuclease-I footprinting was used to analyze 1711 nucleotides of promoter 1 and the entire 328-nucleotide 5'-untranslated region of exon 1, using hepatic nuclear protein extracts from male juvenile hypox rats given a single ip injection of GH or saline 60 min before death. Fourteen DNA-protein binding sites were identified, with 6 located in the highly conserved 5'-untranslated region of exon 1. These latter sites were further characterized for specificity and regulation by GH, using gel mobility shift assays. Two of these DNA-protein interactions were also detected by in vivo dimethylsulfate footprinting. All DNA-protein binding was seen using hepatic nuclear protein extracts from hypox rats and did not change within 15, 30, 60, or 120 min after treatment with GH. Our results thus define a series of constitutive DNA-protein interactions within the major rat IGF-I gene promoter that may be involved in mediating GH-activated nuclear signals to initiate IGF-I transcription.
AB - Insulin-like growth factor-I (IGF-I) is an important mediator of prenatal and postnatal growth, but little is known about the control of IGF-I gene expression. Previously, we demonstrated that GH rapidly stimulates hepatic IGF-I transcription in vivo in hypophysectomized (hypox) rats. In this study, we show that GH induces IGF-I gene transcription through the major promoter, promoter 1, and identify and characterize DNA-protein interactions throughout the promoter. In vitro deoxyribonuclease-I footprinting was used to analyze 1711 nucleotides of promoter 1 and the entire 328-nucleotide 5'-untranslated region of exon 1, using hepatic nuclear protein extracts from male juvenile hypox rats given a single ip injection of GH or saline 60 min before death. Fourteen DNA-protein binding sites were identified, with 6 located in the highly conserved 5'-untranslated region of exon 1. These latter sites were further characterized for specificity and regulation by GH, using gel mobility shift assays. Two of these DNA-protein interactions were also detected by in vivo dimethylsulfate footprinting. All DNA-protein binding was seen using hepatic nuclear protein extracts from hypox rats and did not change within 15, 30, 60, or 120 min after treatment with GH. Our results thus define a series of constitutive DNA-protein interactions within the major rat IGF-I gene promoter that may be involved in mediating GH-activated nuclear signals to initiate IGF-I transcription.
UR - http://www.scopus.com/inward/record.url?scp=0027994214&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0027994214&partnerID=8YFLogxK
U2 - 10.1210/endo.135.4.7925121
DO - 10.1210/endo.135.4.7925121
M3 - Article
C2 - 7925121
AN - SCOPUS:0027994214
SN - 0013-7227
VL - 135
SP - 1584
EP - 1592
JO - Endocrinology
JF - Endocrinology
IS - 4
ER -