Gene amplification in Tetrahymena thermophila: formation of extrachromosomal palindromic genes coding for rRNA.
Gene amplification in Tetrahymena thermophila: formation of extrachromosomal palindromic genes coding for rRNA.
复制标题
嗜热四膜虫的基因扩增：编码 rRNA 的染色体外回文基因的形成。
DOI：
10.1128/mcb.5.6.1260-1267.1985
复制
发表时间：
1985
影响因子：
5.3
通讯作者：
Yao,CH
中科院分区：
文献类型：
--
作者：
Yao,MC;Zhu,SG;Yao,CH
嗜热四膜虫在大核中含有多个染色体外回文基因拷贝，这些基因编码rRNA（rDNA），在发育过程中由单个染色体拷贝产生。在这项研究中，我们分离了rDNA的染色体拷贝，并确定了其5′连接周围序列的结构和发育命运。结果表明，在发育过程中，染色体特异性断裂发生在rDNA的5′连接处或附近。断裂事件与DNA消除和端粒序列添加有关。以前也发现了类似的结果，该基因的3′连接。这些结果可以解释染色体外rDNA是如何首先产生的。在染色体rDNA的两个连接点附近，发现一对20个核苷酸的重复序列，这些序列可能作为位点特异性断裂的信号。另外，在该基因的5′端连接处发现了一对完整的反向重复序列。重复序列长42个核苷酸，间隔28个核苷酸。这种结构的存在为回文rDNA的形成提供了一个简单的解释。
Tetrahymena thermophilacontains in the macronucleus multiple copies of extrachromosomal palindromic genes coding for rRNA (rDNA) which are generated from a single chromosomal copy during development. In this study we isolated the chromosomal copy of rDNA and determined the structure and developmental fate of the sequence surrounding its 5′ junction. The result indicates that specific chromosomal breakage occurs at or near the 5′ junction of rDNA during development. The breakage event is associated with DNA elimination and telomeric sequence addition. Similar results were also found previously for the 3′ junction of this gene. These results could explain how the extrachromosomal rDNA is first generated. Near both junctions of the chromosomal rDNA, a pair of 20-nucleotide repeats was found. These sequences might serve as signals for site-specific breakage. In addition, we found a pair of perfect inverted repeats at the 5′ junction of this gene. The repeats are 42 nucleotides long and are separated by 28 nucleotides. The existence of this structure provides a simple explanation for the formation of the palindromic rDNA.