Autio Kaija J, Kastaniotis Alexander J, Pospiech Helmut, Miinalainen Ilkka J, Schonauer Melissa S, Dieckmann Carol L, Hiltunen J Kalervo
Department of Biochemistry and Biocenter Oulu, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland.
FASEB J. 2008 Feb;22(2):569-78. doi: 10.1096/fj.07-8986. Epub 2007 Sep 26.
In bacteria, functionally related gene products are often encoded by a common transcript. Such polycistronic transcripts are rare in eukaryotes. Here we isolated several clones from human cDNA libraries, which rescued the respiratory-deficient phenotype of a yeast mitochondrial 3-hydroxyacyl thioester dehydratase 2 (htd2) mutant strain. All complementing cDNAs were derived from the RPP14 transcript previously described to encode the RPP14 subunit of the human ribonuclease P (RNase P) complex. We identified a second, 3' open reading frame (ORF) on the RPP14 transcript encoding a protein showing similarity to known dehydratases and hydratase 2 enzymes. The protein was localized in mitochondria, and the recombinant enzyme exhibited (3R)-specific hydratase 2 activity. Based on our results, we named the protein human 3-hydroxyacyl-thioester dehydratase 2 (HsHTD2), which is involved in mitochondrial fatty acid synthesis. The bicistronic arrangement of RPP14 and HsHTD2, as well as the general exon structure of the gene, is conserved in vertebrates from fish to humans, indicating a genetic link conserved for 400 million years between RNA processing and mitochondrial fatty acid synthesis.
在细菌中，功能相关的基因产物通常由一个共同的转录本编码。这种多顺反子转录本在真核生物中很少见。在这里，我们从人cDNA文库中分离出几个克隆，这些克隆挽救了酵母线粒体3-羟酰基硫酯脱水酶2（htd2）突变株的呼吸缺陷表型。所有互补cDNA均来源于先前描述的RPP14转录本，该转录本编码人核糖核酸酶P（RNase P）复合物的RPP14亚基。我们在RPP14转录本上鉴定出第二个3'开放阅读框（ORF），其编码的蛋白质与已知的脱水酶和水合酶2具有相似性。该蛋白质定位于线粒体，重组酶表现出（3R）特异性水合酶2活性。根据我们的结果，我们将该蛋白质命名为人类3-羟酰基硫酯脱水酶2（HsHTD2），它参与线粒体脂肪酸合成。RPP14和HsHTD2的双顺反子排列以及该基因的一般外显子结构在从鱼类到人类的脊椎动物中是保守的，这表明在RNA加工和线粒体脂肪酸合成之间存在4亿年保守的遗传联系。
