人线粒体tRNA修饰碱基与遗传性脑肌病

Human Mitochondrial tRNA Modification and Inherited Encephalomyopathies

人的多种遗传疾病与线粒体tRNA基因突变有关,这些突变导致疾病发生的分子机理是当前研究的热点.通过研究线粒体tRNA分子上的碱基修饰情况,人们发现了一类特殊的带有牛磺酸衍生物基团的修饰,这类修饰主要位于线粒体tRNALys和线粒体tRNALeu(UUR)反密码子第一位摆动(wobble)位点的碱基上.最近的研究表明,位于这两种线粒体tRNA基因上的多种突变与遗传性脑肌病相关,包括A8344G,A3243G,T3271C等等,它们可以导致tRNA上相应摆动位点的碱基修饰缺失.无论是在体外培养的带有相应突变的细胞内,还是在来源于脑肌病病人的组织中,科学家都发现了相同的线粒体tRNA碱基修饰缺陷.通过分子手术证实,此类碱基修饰对于维持这两种tRNA的反密码子与mRNA上相应密码子的相互识别至关重要,缺失了这种修饰的tRNA将无法识别一些对应的密码子.通过进一步的实验,人们还鉴定出负责催化此类碱基修饰的酶.这些研究不但揭示了线粒体遗传性脑肌病相关突变的致病机理,也将为研究基因治疗提供可能的新手段.

Mutations in human mitochondrial tRNA genes are responsible for a variety of human inherited diseases. Investigations of the molecular mechanisms of these diseases are of great interest for nowadays scientists. According to the study of post-transcriptional modification patterns of human mitochondrial tRNAs, novel taurine-containing modifications were identified at the anticodon wobble nucleotides of mitochondrial tRNA^Leu （UUR） and tRNA^Lys. Recently, it was reported that mitochondrial tRNAs harboring one of those encephalomyopathies related mutations, such as A8344G, A3243G, T3271C etc., lacked the normal taurine-containing modification at their anticodon wobble positions. Wobble modification deficiencies of mutant mitochondrial tRNAs were found from cybrid cells, as well as from patient tissues. Molecular surgery experiments showed that the wobble modification is essential for the interaction between the anticodon in tRNA and the codon in mRNA. Furthermore, the enzyme that is responsible for the formation of the modification was identified and characterized. These studies strongly suggested a key molecular factor responsible for the inherited mitochondrial encephalomyopathies and could potentially lead to the development of a gene therapy for these diseases.