Isolation and characterization of the promoter region of the rat DNA topoisomerase IIα gene

A genomic DNA clone containing the 5'-end of the rat topo IIα gene was isolated and the intron/exon structure of a 4.0 kb region encompassing the translation initiation site was determined. Multiple transcription initiation sites were found at positions -128, -110, and -100 bp upstream of the ATG codon. A minimal promoter region extending from -192 to the translation initiation codon was identified on transient expression analysis. This region lacks a TATA motif, is moderately GC-rich and contains a high number of CpG dinucleotides, which is characteristic of a housekeeping gene promoter. The fragment extending to position -242 exhibited maximal promoter activity. Putative regulatory elements were delineated within and immediately upstream of the minimal promoter region. On gel retardation and DNase I footprint analyses, two regions, between positions -195 to -159 which interact with protein factor(s) were identified. The minimal promoter region of the rat topo IIα gene showed high sequence homology with that of human topo IIα. In a 250 bp region upstream of the translation initiation site, the sequence identity was about 70%. The basic structure of the regulatory region of the rat topo IIα gene was found to be similar to that of the human counterpart.