Chaperonin 60 and mitochondrial disease in Dictyostelium
Chaperonin 60 and mitochondrial disease in Dictyostelium
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DOI：
10.1023/a:1024444215766
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发表时间：
2002-10-01
影响因子：
2.7
通讯作者：
Fisher, PR
中科院分区：
文献类型：
--
作者：
Kotsifas, M;Barth, C;Fisher, PR
克隆了网囊藻伴侣蛋白60基因hspA，并对其序列进行了分析。序列比较和三维模型的编码蛋白质的结构表明，它表现出保守的序列和结构特征，预期其作用的Dictyosteremium线粒体伴侣蛋白60。DictyosteoblasthspA含有两个内含子，并且对于这个主要的热休克基因家族的成员来说是不寻常的，它对热、冷或镉离子的反应不是应激诱导的。虽然转录的hspA是下调在早期网骨藻发展响应饥饿，伴侣蛋白60蛋白的水平保持恒定的整个生命周期。与伴侣蛋白60在线粒体生物发生中的重要作用一致，我们无法分离出hspA基因被破坏的突变体。然而，根据基因组中反义表达质粒的拷贝数，分离出表现出不同水平的伴侣蛋白60表达的反义抑制的转化体。在趋光性（和趋热性）的方向严重受损，在所有的反义转化体，而生长和形态发生显着缺陷，只有在转化体具有较高水平的反义抑制。这种表型模式与先前报道的线粒体亚群中线粒体大亚基rRNA基因靶向破坏的结果相似。这表明，无论潜在的遗传缺陷的性质如何，线粒体缺陷比其他细胞活动更敏感地损害信号转导。
The single Dictyostelium chaperonin 60 gene, hspA, was cloned, sequenced and characterized. Sequence comparisons and a three-dimensional model for the structure of the encoded protein showed that it exhibits the conserved sequence and structural features expected for its role as the Dictyostelium mitochondrial chaperonin 60. Dictyostelium hspA contains two introns and, unusually for a member of this major heat shock gene family, is not stress-inducible in response to heat, cold or cadmium ions. Although transcription of hspA is down regulated during early Dictyostelium development in response to starvation, the levels of the chaperonin 60 protein remain constant throughout the life cycle. Consistent with the essential role of chaperonin 60 in mitochondrial biogenesis, we were unable to isolate mutants in which the hspA gene had been disrupted. However, transformants were isolated that exhibited differing levels of antisense inhibition of chaperonin 60 expression, depending upon the number of copies of the antisense-expressing plasmid in the genome. Orientation in phototaxis ( and thermotaxis) was severely impaired in all antisense transformants, while growth and morphogenesis were markedly defective only in transformants with higher levels of antisense inhibition. This pattern of phenotypes is similar to that reported previously to result from targeted disruption of the mitochondrial large subunit rRNA gene in a subpopulation of mitochondria. This suggests that, regardless of the nature of the underlying genetic defect, mitochondrial deficiency impairs signal transduction more sensitively than other cellular activities.