Biochemical and functional properties of a palindromic sequence motif within the hepatitis B virus enhancer 1.
The hepatitis B virus (HBV) enhancer 1 is a transcriptional element that contributes to the liver-specific regulation of HBV gene expression. We previously identified a novel protein binding site within the enhancer that contains an 8-bp palindromic sequence motif. This motif partially overlaps the binding sites for nuclear factor 1 and hepatocyte nuclear factor 3beta (HNF3beta). Moreover, we demonstrated that this novel site is recognized by a protein or proteins, tentatively designated as palindrome-binding factor (PBF), that cooperatively interact with HNF3beta. In the present work, we have further examined the biochemical and functional attributes of PBF. Protein-DNA interaction studies indicate that three thymidine residues located at the 3'-end of the palindromic sequence motif are important for maximal PBF-binding activity. When protein-DNA complexes were photocrosslinked by exposure to ultraviolet (UV) light, a prominent polypeptide with an apparent molecular mass of 50 kDa was found to associate with the PBF-binding site. Furthermore, transient transfection studies support the hypothesis that PBF contributes to enhancer 1 activity by a combinatorial mechanism that involves at least one other cis-acting sequence motif, the HNF3beta-binding site.
Kosovsky
M J
MJ
Department of Microbiology and Program in Molecular Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
Siddiqui
A
A
D004742:Enhancer Elements, Genetic / Q000235:genetics*; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics
D014157:Transcription Factors