Liver-specific expression of human insulin-like growth factor binding protein 1: functional role of transcription factor HNF1 in vivo.
Tissue-specific expression of insulin-like growth factor binding protein 1 (IGFBP-1) in the liver has been studied using differentiated (H4II and C2Rev7) and dedifferentiated (H5 and C2) rat hepatoma cell lines. Northern blot analysis showed that endogenous IGFBP-1 mRNA was expressed only in the differentiated cell lines. The first 341 base pairs 5' to the transcription initiation site of the human IGFBP-1 gene were inserted upstream of the chloramphenicol acetyltransferase reporter gene (pBP-1(341)). Expression of this gene from the human IGFBP-1 promoter was 10-16 times more efficient in the H4II line than in the other hepatoma cell lines and 40 and approximately 12 times more so than in rat fibroblasts (FR3T3) and a human cervical carcinoma cell line (C33), respectively. Cotransfection of pBP-1(341) and pRSV-HNF1 and/or pRSV-v-HNF1 (eukaryotic expression vectors that drive the synthesis of the liver-enriched trans-acting factor HNF1 or of v-HNF1, a related form) in C33 recipient cells yielded a 6-fold increase in IGFBP-1 promoter activity by HNF1 and a 2-fold increase by v-HNF1. These increases were dependent on the integrity of an HNF1 binding site located 58-74 nucleotides upstream of the cap site. Stimulation of promoter activity by cotransfection of both HNF1 and v-HNF1 fell between these values. Our results indicate that HNF1 is instrumental in human IGFBP-1 promoter activity in vivo and that v-HNF1 modulates this functional role.
Babajko
S
S
Unité de Recherches sur la Régulation de la Croissance, Institut National de la Santé et de la Recherche Médicale U.142, Hôpital Saint Antoine, Paris, France.
Tronche
F
F
Groyer
A
A
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D005822:Genetic Vectors; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1; D008099:Liver / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D013002:Somatomedins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; C496489:Hnf1a protein, rat; D018970:Insulin-Like Growth Factor Binding Protein 1; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D013002:Somatomedins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta