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首页> 外文期刊>Molecular and Cellular Biology >Hyperactive recombination in the mitochondrial DNA of the natural death nuclear mutant of Neurospora crassa.
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Hyperactive recombination in the mitochondrial DNA of the natural death nuclear mutant of Neurospora crassa.

机译：Neurospora crassa自然死亡核突变体的线粒体DNA中的过度活跃重组。

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摘要

In Neurospora crassa, a recessive mutant allele of a nuclear gene, nd (natural death), causes rapid degeneration of the mitochondrial DNA, a process that is manifested phenotypically as an accelerated form of senescence in growing and stationary mycelia. To examine the mechanisms that are involved in the degradation of the mitochondrial chromosome, several mitochondrial DNA restriction fragments unique to the natural-death mutant were cloned and characterized through restriction, hybridization, and nucleotide sequence analyses. All of the cloned DNA pieces contained one to four rearrangements that were generated by unequal crossing-over between direct repeats of several different nucleotide sequences that occur in pairs and are dispersed throughout the mitochondrial chromosome of wild-type Neurospora strains. The most abundant repeats, a family of GC-rich sequences that includes the so-called PstI palindromes, were not involved in the generation of deletions in the nd mutant. The implication of these results is that the nd allele hyperactivates a general system for homologous recombination in the mitochondria of N. crassa. Therefore, the nd+ allele either codes for a component of the complex of proteins that catalyzes recombination, and possibly repair and replication, of the mitochondrial chromosome or specifies a regulatory factor that controls the synthesis or activity of at least one enzyme or ancillary factor that is affiliated with mitochondrial DNA metabolism.
机译：在神经孢霉中，核基因的隐性突变等位基因nd（自然死亡）会导致线粒体DNA迅速变性，这种现象在表型上表现为生长和静止的菌丝体中衰老的加速形式。为了检查与线粒体染色体降解有关的机制，克隆了几个自然死亡突变体特有的线粒体DNA限制片段，并通过限制，杂交和核苷酸序列分析对其进行了表征。所有克隆的DNA片段都包含1-4个重排，这些重排是通过成对出现并分散在野生型Neurospora菌株的线粒体染色体上的几个不同核苷酸序列的直接重复之间的不相等交叉产生的。最丰富的重复序列是一个富含GC的序列家族，其中包括所谓的PstI回文序列，不涉及nd突变体中缺失的产生。这些结果的暗示是nd等位基因过度激活了克雷萨氏菌线粒体中同源重组的一般系统。因此，nd +等位基因要么编码催化线粒体染色体重组并可能修复和复制的蛋白质复合物的成分，要么指定控制至少一种酶或辅助因子的合成或活性的调节因子。与线粒体DNA代谢有关。

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