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BAP, a rat liver protein that activates transcription through a promoter element with similarity to the USF/MLTF binding site

1990; Oxford University Press; Volume: 18; Issue: 23 Linguagem: Inglês

10.1093/nar/18.23.6943

1362-4962

Wilfried Kugler, Michael Kaling, Ulrike Wagner, Gerhart U. Ryffel,

Hepatitis B Virus Studies

The vitellogenin genes of Xenopus are llver-specifically expressed. An in vitro transcription system derived from rat liver nuclei allowed us to define the cis-element BABS (B-activator binding site) in the promoter of the B1 vitellogenin gene. An oligonucleotide encompassing the region from – 53 to –44 linked to a TATA box is sufficient for a tenfold increase of the transcriptional activity. Gel retardation assays with nuclear rat liver proteins reveal two DNA-protein complexes: Complex 1 can be competed by the USF/MLTF binding site of the adeno major late promoter whereas complex 2 is a distinct protein we refer to as BAP (B-actlvator protein). In vitro transcription experiments in the presence of USF/MLTF binding site as competitor show that BAP is an efficient transcription factor. Based on UV crosslinking we estimate that BAP has a molecular weight of 58 kd. Phosphatase treatment reveals that DNA binding of BAP requires phosphorylation. BABS is also present in the hepatitis B virus enhancer suggesting that it might play a role in the tumorigenic potential of the virus.