Tremblay G B, Sohi S S, Retnakaran A, MacKenzie R E
Department of Biochemistry, McGill University, Montreal, QC, Canada.
FEBS Lett. 1995 Jul 10;368(1):177-82. doi: 10.1016/0014-5793(95)00640-u.
Cytosolic NADP-dependent methylenetetrahydrofolate dehydrogenase-cyclohydrolase synthetase and the mitochondrial NAD-dependent methylenetetrahydrofolate dehydrogenase-cyclohydrolase (NMDMC) are differentially expressed during insect development although both enzymes are detectable at all stages. In contrast, cell lines derived from a variety of insect species express high levels of NMDMC but undetectable levels of the NADP-dependent enzyme. Northern analysis indicates the NMDMC message is expressed at levels 50-100 times higher in a Drosophila cell line compared to adult flies. RNase protection showed the predominance of shortened transcripts that require initiation at a downstream AUG producing a truncated protein that lacks a mitochondrial targeting sequence. These changes in expression effectively exchange the cytosolic NADP-dependent dehydrogenase for one with NAD specificity.
胞质NADP依赖性亚甲基四氢叶酸脱氢酶-环水解酶合成酶和线粒体NAD依赖性亚甲基四氢叶酸脱氢酶-环水解酶（NMDMC）在昆虫发育过程中差异表达，尽管这两种酶在所有阶段都可检测到。相比之下，源自多种昆虫物种的细胞系表达高水平的NMDMC，但未检测到NADP依赖性酶的水平。Northern分析表明，与成年果蝇相比，果蝇细胞系中NMDMC信息的表达水平高50-100倍。RNase保护显示，缩短的转录本占优势，这些转录本需要在下游AUG起始，产生一种缺乏线粒体靶向序列的截短蛋白。这些表达变化有效地将胞质NADP依赖性脱氢酶换成了具有NAD特异性的脱氢酶。
