STRUCTURAL ORGANIZATION OF THE MOUSE DNA-REPAIR GENE, N-METHYLPURINE-DNA GLYCOSYLASE

N-Methylpurine-DNA glycosylase (MPG), a ubiquitous DNA repair enzyme, removes N-alkylpurines and other purine lesions induced in DNA by simp le alkylating carcinogens, A mouse MPG cDNA clone was isolated from a lambda recombinant phage library of BALB/c mouse lung cell and charact erized, Using the mouse MPG cDNA as a probe, the complete mouse MPG ge ne was isolated in two overlapping lambda recombinant genomic clones. The 6-kb gene has four exons containing 1,002 bp of coding sequence. T he transcription start site was identified in the genomic sequence by primer extension of MPG mRNA from a mouse lung fibroblast cell line, T he location of this transcription start site was confirmed by in vitro transcription with the promoter-containing plasmid template. Promoter function of the sequence 5' upstream of the transcription initiation site was shown by transient expression of the firefly luciferase repor ter gene under the control of this sequence in transfected human and m ouse cells, The mouse MPG promoter contains no TATA box, but has a CAA T element and is G.C-rich with putative AP2 elements and SP1-complemen tary sequences.