THE hepatitis B virus (HBV) X gene product (pX) could be important in disease pathogenesis because it is known to transacti-vate transcription from many viral and cellular gene promoters1-8, including the HBV core gene promoter, the human immunodeficiency virus (HIV-1) long terminal repeat, and the c-myc promoter. We have previously shown that only a subset of the promoters that can be transactivated by pX is transactivated in any particular cell line, and have proposed that pX acts through multiple, cell type-specific transcription factors9. We show here that pX acts through both AP-1 and AP-2 sites, and that pX has a transcription activation domain. We conclude that transactiva-tion by pX depends on at least two distinct cellular DNA-binding transcription factors and we present a model for the action of pX.
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