Abstract
There are two forms of monoamine oxidase (MAO, E.C.1,4,3,4) in human, named MAOA and MAOB. Both of the two genes have been localized in the p11.23 region of X chromosome, and they are localized in the outer membrane of mitochondria, where they oxidize catecholamine and indolamine neurotransmitters and other biogenic amines. Although the two forms of MAO have 73% similarity in amino acid sequences and catalyze the same reaction, they are different in tissue distribution and specificities for substrates and inhibitors. MAOA preferentially catalyzes oxidative deamination of serotonin, norepinephrine and epinephrine. It is sensitive to inhibition by the acetylenic inhibitor clorgyline. MAOB preferentially catalyzes the degradation of phenylethylamine and benzylamine. It is sensitive to inhibition by the irreversibly inhibitor pargyline and deprenyl. Dopamine, tyramine and tryptamine are common substrates for both of them.The mechanism for regulation of MAOA expressionis still unclear. In previous studies, researchers find that some repeat sequences in MAOA promoter region. We also found polymorphisms in one of them, which are localized from -1143 to -1262. The effect of these repeats and flanking sequences on MAOA gene expression was studied. A 1.4Kb 5'-noncoding region of MAOA was fused to a luciferase reporter gene ( pGL3-Enhancer Luciferase Vector ) and transient transfections into mammalian cell lines were done for analysis of different alleles of MAOA in the promoter region.A previous study showed that the upstream sequence down regulates the reporter genes expression. Our result showed that the number of repeats may affect gene as well as expression the tissue specificity. This implies that these direct repeats in MAOA promoter region may play an important role in the regulation of gene expression.