Klein R D, Favreau M A
Molecular Biology Research, Upjohn Company, Kalamazoo, MI 49007.
Gene. 1991 Jan 15;97(2):183-9. doi: 10.1016/0378-1119(91)90050-l.
A 4.05-kb DNA fragment containing the ADE2 gene from Schwanniomyces occidentalis was cloned into the pUC19 vector. When an ade2 strain of Sc. occidentalis was transformed with this plasmid, pADE-2 was found to integrate into the host chromosome and was also present in a variety of extrachromosomal species. These extrachromosomal elements were present in multiple copies, varied in molecular mass and were composed of polymerized forms of pADE-2. A fragment containing the ADE2 gene was used to transform a Sc. occidentalis ade2 mutant, as either a linear or circularized molecule. The linear form integrated into the host genome, whereas the circularized form was found as a stably maintained extrachromosomal element with no evidence of integration or detectable loss of the Ade+ phenotype upon subculturing of transformed yeast under nonselective conditions for 60 generations. The ratio of the number of extrachromosomal ADE2 genes to genomic ADE2 ranged from 3.8 to 6.6.
将一段含有西方许旺酵母ADE2基因的4.05 kb DNA片段克隆到pUC19载体中。当用该质粒转化西方许旺酵母的ade2菌株时，发现pADE - 2整合到宿主染色体中，并且也存在于多种染色体外形式中。这些染色体外元件以多拷贝形式存在，分子量各异，由pADE - 2的聚合形式组成。用一个含有ADE2基因的片段作为线性或环化分子来转化西方许旺酵母ade2突变体。线性形式整合到宿主基因组中，而环化形式则作为稳定维持的染色体外元件被发现，在非选择性条件下对转化酵母进行60代传代培养后，没有整合的证据或Ade +表型的可检测损失。染色体外ADE2基因数量与基因组ADE2数量的比例范围为3.8至6.6。
