THE TATA-LESS PROMOTER OF HEPATITIS-B VIRUS S-GENE CONTAINS A TBP BINDING-SITE AND AN ACTIVE INITIATOR

The surface antigen (S) gene promoter, one of the major hepatitis B vi rus (HBV) promoters, directs the synthesis of a 2.1 kb mRNA which enco des the preS2 and S polypeptides. The preS2/S promoter does not contai n a classical TATA box, and transcription regulation of the preS2/S ge ne has not been fully elucidated. We analysed two regions involved in preS2/S gene transcription of the HBV adw subtype: the diverged TATA b ox and a putative initiator element. We demonstrated sequence specific promoter activity of the putative TATA-like sequences in the preS2/S gene promoter (- 25 to - 32 bp). Using end labeled synthetic oligonucl eotides we observed specific binding of nuclear extracts to the diverg ed TATA sequence, that was significantly reduced using a mutated oligo nucleotide. Specific binding of yeast TBP to the diverged TATA sequenc e was shown which was increased in the mutant containing a classical T ATA box. We analysed the proposed initiator (Inr) sequence of the preS 2/S promoter region (-13 to - 16 bp). Deletion of the Inr element mark edly reduced promoter activity as assessed by CAT expression. Gel shif t assays showed specific binding of nuclear extracts to wild type but not to mutant Inr. Expression studies with double mutants of the diver ged TATA and the Inr element established that both elements are active in transcription regulation. (C) 1997 Elsevier Science B.V.