J. Virol., Dec 1996, 8571-8583, Vol 70, No. 12
Copyright © 1996, American Society for Microbiology
G Fourel, F Ringeisen, M Flajolet, F Tronche, M Pontoglio, P Tiollais and MA Buendia
Unite de Recombinaison et Expression Genetique, INSERM U163, Institut Pasteur, Paris, France.
Transcriptional activation of myc family proto-oncogenes through the insertion of viral sequences is the predominant mechanism by which woodchuck hepatitis virus (WHV) induces liver tumors in chronically infected animals. The main target is N-myc2, a functional retroposon of the N-myc gene, but c-myc and N-myc are also marginally involved. Here we identify a major, liver-specific regulatory element in the WHV genome (We2) which efficiently activates the N-myc2 promoter in cultured hepatoma cells. In the context of the episomal viral genome, We2 governs the production of pregenomic RNA and thus plays a central role in the control of viral replication. We2 activity is primarily controlled by the liver-enriched HNF1 and HNF4 transcription factors, although NF1 and Oct proteins were also shown to bind in a central region. The expression of HNF1 and HNF4 appears to be maintained in woodchuck tumors. Thus, We2 is a prime candidate for controlling myc gene cis activation during WHV-induced hepatocarcinogenesis.
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