LFB1/HNF1 acts as a repressor of its own transcription.
LFB1/HNF1 is a hepatocyte-enriched trans-activator involved in the regulation of many liver-specific genes. We report the cloning and characterization of a rat genomic DNA fragment containing about 3.5 kb of the LFB1/HNF1 gene 5'-flanking region. This DNA segment is capable of directing the liver-specific expression of a reporter gene in transfection assays. More interestingly, the basal activity of the LFB1/HNF1 promoter in cultured hepatoma cell lines is down-regulated by exogenously added LFB1/HNF1 protein itself. The ability to repress transcription starting from its own promoter requires the integrity of the N-terminal LFB1/HNF1 DNA-binding domain. Contrary to the expectations, in vitro binding experiments failed to demonstrate any specific and functional interaction of purified LFB1/HNF1 with the -3.5 kb promoter sequence. In addition to the DNA-binding domain, a 60 aa region contained in the C-terminus of the protein and distinct from the previously characterized activation domains, is also required for the repressing function.
Piaggio
G
G
Istituto Regina Elena Centro Ricerca Sperimentale, Laboratorio Oncogenesi Molecolare, Rome, Italy.
Tomei
L
L
Toniatti
C
C
De Francesco
R
R
Gerstner
J
J
Cortese
R
R
D000818:Animals; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004247:DNA / Q000378:metabolism; D015342:DNA Probes; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D006367:HeLa Cells; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D008113:Liver Neoplasms; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D051381:Rats; D012097:Repressor Proteins; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D015342:DNA Probes; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; C496489:Hnf1a protein, rat; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase