ANALYSIS OF TISSUE-SPECIFIC AND DEVELOPMENTALLY REGULATD EXPRESSION OF THE GENE ENCODING ADENYLATEKINASEISOZYMES

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Adenylate kinase(AK) is a ubiquitous enzyme which contributes to homeostasis of the cellular adenine nucleotide composition. Three isozymes(AK1, AK2 and AK3) have been characterized in vertebrates. AK1 is present in the cytosol of skeletal muscle, brain and erythrocytes, whereas AK2 is found in the mitochondrial intermembrane space of liver, kidney, spleen and heart. AK1 and AK2 catalyze the reaction ; Mg+ATP+AMP(〕SY.dblharw.〔)Mg+ADP+ADP.AK3, which catalyzes the reaction ; Mg+GTP+AMP(〕SY.dblharw.〔)Mg+GDP+ADP, is present in the mitochondrial matrix of many tissues. The aim of this research is to elucidate the physiological role of these isozymes. For this purpose, we nees to define the distribution of these isozymes and the localization in the cells. Therefore, we have previously isolated the genes encoding chicken AK1, human AK1, bovine AK2 and bovine AK3. In this research, we were successful in isolating the 5'-flanking region of the human AK1 and AK3 genes and characterized them. The 5'-flanking region of the AK1 gene contains TATA box and the expression of AK1 gene is inducible during muscle differentiation in vitro. The 5'-flanking region of the human AK3 gene lacks both TATA and CAAT boxes. THe G+C contents of this region is as high as 71%, and eight GC boxes are present. The promoter region of this gene showed a structure similar to those of house-keeping genes. Although information on the mechanism of transcription initiation of the TATA-containing genes has been accumulated, little is known about the transcriptional regulation of TATA-less house-keeping genes such as the AK3 gene. Comparison of its promoter sequence with that of the bovine AK3 gene showed the presence of four significant homologous stretches of 12-14nucleotides. We analyzed the effect of deletion in the upstream regions of the human and bovine AK3 genes on the transcriptional activity. Further, the homolougous regions containing the putative regulatory elements were tested for their ability