Transcription of the beta2-adrenergic receptor gene in rat liver is regulated during early postnatal development by an upstream repressor element.
As early postnatal development of the male rat proceeds, there is a decline in transcription of the beta2-adrenergic receptor gene in liver which is associated with a decline in beta2-adrenergic receptor mediated glucose mobilization. In this study, primary cultures of rat hepatocytes transiently transfected with fusion genes containing various segments of beta2-adrenergic receptor gene 5'-flanking DNA fused to a promoterless luciferase reporter gene were used to identify genetic elements that might control beta2-adrenergic receptor gene expression during the first 10 days of postnatal life. We found that 261 bp of beta2-adrenergic receptor gene 5'-flanking region (-372 to -95, start of translation is +1) was sufficient to direct high luciferase expression in fetal day 18 hepatocytes and therefore included the beta2-adrenergic receptor gene promoter. Luciferase activities in fetal day 18 hepatocytes transfected with pbeta2AR(-372/-95), pbeta2AR(-1,335/-95) and pbeta2AR(-3,349/-95) were fourfold greater than that in either postnatal day 5 or postnatal day 10 hepatocytes transfected with the same fusion genes. By use of gel mobility shift assays, we observed increased protein binding to a 50 bp segment (-372 to -323) of the beta2-adrenergic receptor gene 5'-flanking region with nuclear extracts prepared from postnatal day 5 and postnatal day 10 hepatocytes compared to fetal day 18 hepatocytes. These findings suggest the presence of a regulatory element in the 5'-flanking region of the beta2-adrenergic receptor gene that appears to be involved in suppression of transcription of the beta2-adrenergic receptor gene in liver during early postnatal development.
Baeyens
D A
DA
Department of Biology, University of Arkansas at Little Rock, USA.
McGraw
D W
DW
Jacobi
S E
SE
Cornett
L E
LE
D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002457:Cell Extracts; D002467:Cell Nucleus; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005796:Genes / Q000235:genetics; D008099:Liver / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics*; D011993:Recombinant Fusion Proteins; D014158:Transcription, Genetic / Q000235:genetics*; D014162:Transfection; D014466:Ultraviolet Rays
D002457:Cell Extracts; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D018343:Receptors, Adrenergic, beta-2; D011993:Recombinant Fusion Proteins; D004247:DNA