ORGANIZATION, SEQUENCE, AND EXPRESSION OF THE MURINE S100-BETA GENE -TRANSCRIPTIONAL REGULATION BY CELL-TYPE-SPECIFIC CIS-ACTING REGULATORY ELEMENTS

The organization, sequence, and transcriptional regulation of expressi on of the murine S100beta gene are reported. The gene is approximately 9 kilobase pairs in length and is composed of three exons and two int rons. The deduced murine S100beta protein sequence differs from the hu man S100beta protein by only 1 amino acid. The murine S100beta gene co ntains a TATA box (AATAA) and a reverse CCAAT box (ATTGG) located at 3 0 nucleotides and 92 nucleotides upstream of the cap site, respectivel y. A 149-base pair DNA fragment (-157/-9) spanning the TATA box and th e reverse CCAAT box functions as a promoter. The murine S100beta promo ter drives a 4-fold higher level of transcription in glial (C6) than i n non-glial (3T3) cells, suggesting the existence of a potential cell type-specific regulatory element within the promoter region. The 5'-fl anking region suppresses transcription from the homologous S100beta as well as the heterologous SV40 promoters in an orientation-independent fashion. However, the 5'-flanking region exhibits cell type specifici ty when suppressing the S100beta promoter-dependent transcription, ind icating its involvement in the cell type-specific expression of S100be ta gene. In order to map cell type-specific regulatory elements, trans cription analyses of various deletions of the 5'-region were carried o ut in C6 and 3T3 cells. Two cell type-specific negative regulatory ele ments, one active in non-glial cells and another active in glial cells , were mapped to the regions -1552/-1234 and -1234/-551, respectively. A strong negative regulatory element and a relatively weak negative e lement were located in the regions -551/-157 and -1669/-1552, respecti vely. The murine S100beta gene is under complex transcriptional regula tion involving tonic negative control exerted by combination of multip le cis-acting regulatory elements including cell type-specific element s.