Abstract
We have isolated a human ornithine decarboxylase (ODC) gene from a leukocyte genomic DNA library in order to examine the mechanisms involved in the regulation of ODC gene expression in normal and neoplastic cell growth. Nucleotide sequence analysis shows that the human ODC gene in clone ODC709-A2 consists of 12 exons which encode a protein identical to that inferred from a human ODC cDNA sequence. The 5' end of the gene was determined by S1 nuclease and primer extension mapping. The high G + C content and small open reading frame found in exon 1 may be pertinent to translation regulation of ODC. Conserved sequences and potential promoter elements including a TATA box, a possible CCAAT element, SP1 and AP-2 transcription factor binding sites, and cAMP response elements were identified in the 5'-flanking region. Transfection of mouse LM (tk-) cells with ODC709-A2 DNA resulted in the production of human ODC mRNA approximately 2.25 kilobases in length. Evidence that the protein synthesized from the human gene is functional is provided by "rescue" transfection of a Chinese hamster ovary mutant cell line, C55.7, which is ODC-deficient. C55.7 cells transfected with ODC709-A2 DNA expressed ODC enzyme activity and proliferated without exogenous putrescine.
Highlights
Nucleotide sequence analysis shows that the human ornithine decarboxylase (ODC) gene in clone ODC709-A2 consists of 12 exons which encode a protein identical to that inferred from a human ODC cDNA sequence
Intracellular polyamine concentrations are highly regulated by the enzyme ornithine decarboxylase (ODC,’ EC 4.1.1.17), which catalyzes the conversion of ornithine to putrescine, the initial and often ratelimiting step in polyamine biosynthesis
We report here the isolation and characterization of a human gene encoding a functional ODC enzyme as the initial phase of our investigation into the basic mechanisms controlling the expression of the human ODC gene
Summary
Molecular probes in the form of mouse (Berger et al, 1984; Kahana and Nathans, 1984; Kontula et al, 1984; M~Conlo~a et at., 1984; Kahana and Nathans, 1985b), rat (van Kranen et d, 1987), and human (Hickok et al, 1987) ODC cDNA clones have been developed to examine the regulation of ODC synthesis at the level of gene transcription. These studies have shown that some bosh-stimulating agents enhance ODC synthesis by increasing either the rate of gene transcription or the stabilization of ODC mRNA. We report here the isolation and characterization of a human gene encoding a functional ODC enzyme as the initial phase of our investigation into the basic mechanisms controlling the expression of the human ODC gene
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