Suppression of a mitochondrial tRNA gene mutation phenotype associated with changes in the nuclear background
Suppression of a mitochondrial tRNA gene mutation phenotype associated with changes in the nuclear background
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DOI：
10.1093/hmg/8.6.1117
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发表时间：
1999-06-01
影响因子：
3.5
通讯作者：
Moraes, CT
中科院分区：
文献类型：
--
作者：
Hao, HL;Morrison, LE;Moraes, CT
我们以前已经鉴定了tRNA(ASN)基因中的一个致病性mtDNA突变，该突变(G5703A)与严重的线粒体蛋白质合成缺陷和tRNA(ASN)的稳态水平降低有关。我们现在表明，尽管携带同质突变水平的传递线粒体胞质不能在半乳糖介质中存活，但可以获得几个抗半乳糖的克隆。这些细胞株恢复了氧化磷酸化功能，tRNA(Asn)的稳态水平比亲本突变株高2倍，突变株具有明显的同质突变水平，tRNA(Asn)基因没有其他可检测到的变化。为了研究这种抑制的来源，我们将mtDNA从回复突变体(143B/206TK-)转移到不同的核背景(143B/207TK-，8AG(R))，这些新的线粒体环体再次发生氧化磷酸化缺陷，恢复了对半乳糖的敏感性。然而，也可以通过培育所选择的8AG(R)传递线粒体杂交体获得半乳糖抗性克隆。由于原始的返回率高于经典的第二位点核突变的预期，而且由于这些细胞系的非整倍体特征，我们寻找可能与突变表型相关的染色体改变的存在，然而，这些研究没有揭示任何重大变化。我们的结果表明，调节未知核编码因子(S)的剂量或表达可以补偿致病线粒体tRNA基因突变，为治疗干预提供新的策略。
We previously have characterized a pathogenic mtDNA mutation in the tRNA(Asn) gene, This mutation (G5703A) was associated with a severe mitochondrial protein synthesis defect and a reduction in steady-state levels of tRNA(Asn). We now show that, although transmitochondrial cybrids harboring homoplasmic levels of the mutation do not survive in galactose medium, several galactose-resistant clones could be obtained. These cell lines had restored oxidative phosphorylation function and 2-fold higher steady-state levels of tRNA(Asn) when compared with the parental mutant cell line, The revertant lines contained apparently homoplasmic levels of the mutation and no other detectable alteration in the tRNA(Asn) gene. To investigate the origin of the suppression, we transferred mtDNA from the revertants (143B/206 TK-) to a different nuclear background (143B/207 TK-, 8AG(r)), These new transmitochondrial cybrids became defective once again in oxidative phosphorylation and regained galactose sensitivity. However, galactose-resistant clones could also be obtained by growing the 8AG(r) transmitochondrial cybrids under selection. Because the original rate of reversion was higher than that expected by a classic second site nuclear mutation, and because of the aneuploid features of these cell lines, we searched for the presence of chromosomal alterations that could be associated with the revertant phenotype, These studies, however, did not reveal any gross changes. Our results suggest that modulation of the dosage or expression of unknown nuclear-coded factor(s) can compensate for a pathogenic mitochondrial tRNA gene mutation, suggesting new strategies for therapeutic intervention.