ISOLATION AND CHARACTERIZATION OF THE PROMOTER REGION OF THE RAT DNA TOPOISOMERASE II-ALPHA GENE

A genomic DNA clone containing the 5'-end of the rat topo IIalpha gene was isolated and the intron/exon structure of a 4.0 kb region encompa ssing the translation initiation site was determined, Multiple transcr iption initiation sites were found at positions -128, -110, and -100 b p upstream of the ATG codon, A minimal promoter region extending from -192 to the translation initiation codon was identified on transient e xpression analysis, This region lacks a TATA motif, is moderately GC-r ich and contains a high number of CpG dinucleotides, which is characte ristic of a housekeeping gene promoter, The fragment extending to posi tion -242 exhibited maximal promoter activity, Putative regulatory ele ments were delineated within and immediately upstream of the minimal p romoter region, On gel retardation and DNase I footprint analyses, two regions, between positions -195 to -159 which interact with protein f actor(s) were identified. The minimal promoter region of the rat topo IIalpha gene showed high sequence homology with that of human topo IIa lpha. In a 250 bp region upstream of the translation initiation site, the sequence identity was about 70%, The basic structure of the regula tory region of the rat topo IIalpha gene was found to be similar to th at of the human counterpart.