Expression of the gene encoding human brain creatine kinase depends on sequences immediately following the transcription start point.

To localize sequences that are important for regulation of the gene (CK-B) encoding human brain creatine kinase (CK-B), we have functionally dissected the region comprising 1.8 kb of DNA upstream from the main transcription start point (tsp) and the first exon and intron, and made a detailed comparison with the situation in the rat CK-B gene. Upon using the transient chloramphenicol acetyltransferase (CAT) assay in human HeLa and mouse neuroblastoma cells, we have delimited the basal promoter in the human CK-B gene to a segment of 150 nucleotides (nt) immediately preceding the major mRNA cap site. No other essential regulatory sequence is located further upstream. Both from tsp mapping and from mutational inactivation studies, we conclude that of the two T + A-rich motifs in the promoter region, the TTAA motif between nt positions -28 to -25 is of major importance for transcriptional activity. Moreover, and most notably, a region spanning 22 nt of the first exon has a strong stimulatory effect on CK-B/CAT synthesis.