RFX1 is identical to enhancer factor C and functions as a transactivator of the hepatitis B virus enhancer.
Hepatitis B virus gene expression is to a large extent under the control of enhancer I (EnhI). The activity of EnhI is strictly dependent on the enhancer factor C (EF-C) site, an inverted repeat that is bound by a ubiquitous nuclear protein known as EF-C. Here we report the unexpected finding that EF-C is in fact identical to RFX1, a novel transcription factor previously cloned by virtue of its affinity for the HLA class II X-box promoter element. This finding has allowed us to provide direct evidence that RFX1 (EF-C) is crucial for EnhI function in HepG2 hepatoma cells; RFX1-specific antisense oligonucleotides appear to inhibit EnhI-driven expression of the hepatitis B virus major surface antigen gene, and in transfection assays, RFX1 behaves as a potent transactivator of EnhI. Interestingly, transactivation of EnhI by RFX1 (EF-C) is not observed in cell lines that are not of liver origin, suggesting that the ubiquitous RFX1 protein cooperates with liver-specific factors.
Siegrist
C A
CA
Department of Genetics and Microbiology, University of Geneva Medical School, Switzerland.
Durand
B
B
Emery
P
P
David
E
E
Hearing
P
P
Mach
B
B
Reith
W
W
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004279:DNA, Viral; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009928:Organ Specificity / Q000235:genetics; D000071701:Regulatory Factor X Transcription Factors; D000071716:Regulatory Factor X1; D012091:Repetitive Sequences, Nucleic Acid; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000378:metabolism
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D016376:Oligonucleotides, Antisense; C000605537:RFX1 protein, human; D000071701:Regulatory Factor X Transcription Factors; D000071716:Regulatory Factor X1; C000605538:Rfx1 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D014759:Viral Envelope Proteins