UNSTABLE DNA AMPLIFICATIONS IN METHOTREXATE-RESISTANT LEISHMANIA CONSIST OF EXTRACHROMOSOMAL CIRCLES WHICH RELOCALIZE DURING STABILIZATION
UNSTABLE DNA AMPLIFICATIONS IN METHOTREXATE-RESISTANT LEISHMANIA CONSIST OF EXTRACHROMOSOMAL CIRCLES WHICH RELOCALIZE DURING STABILIZATION
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DOI：
10.1016/0092-8674(84)90498-7
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发表时间：
1984-01-01
期刊：
影响因子：
64.5
通讯作者：
SCHIMKE, RT
中科院分区：
文献类型：
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作者：
BEVERLEY, SM;CODERRE, JA;SCHIMKE, RT
甲氨蝶呤抗性热带乳杆菌含有 2 个独立的 DNA 扩增区域，一个编码原生动物特有的双功能胸苷酸合成酶-二氢叶酸还原酶 (TS-DHFR)，另一个功能尚不清楚。扩增的 DNA 最初被发现为染色体外闭合环状形式，在没有选择的情况下不稳定。在甲氨蝶呤中长时间培养后，经 CsCl-溴化乙锭密度梯度离心后，发现扩增的 DNA 为与染色体 DNA 级分相关的重复阵列，并且一旦去除选择就稳定。利什曼原虫基因扩增的分子描述与培养的哺乳动物细胞中基因扩增的细胞学特征非常相似。
Methotrexate-resistant L. tropica contain 2 separate regions of DNA amplification, one encoding the bifunctional thymidylate synthetase-dihydrofolate reductase (TS-DHFR) characteristic of protozoans and the other of yet unknown function. The amplified DNA are initially found as extrachromosomal closed circular forms, which are unstable in the absence of selection. After prolonged culture in methotrexate the amplified DNA are found as repetitive arrays associated with the chromosomal DNA fraction after CsCl-ethidium bromide density gradient centrifugation and are stable once selection is removed. The molecular description of gene amplification in Leishmania closely parallels the cytological features of gene amplification in cultured mammalian cells.