Gunge N, Murakami K, Takesako T, Moriyama H
Kumamoto Institute of Technology, Department of Applied Microbial Technology, Japan.
Yeast. 1990 Sep-Oct;6(5):417-27. doi: 10.1002/yea.320060507.
The linear killer plasmids, pGKL1 and pGKL2, from Kluyveromyces lactis stably replicated in mitochondrial DNA-deficient (rho 0) MATa or MAT alpha haploids of Saccharomyces cerevisiae, but were unstable and frequently lost in rho 0 MATa/MAT alpha diploids, suggesting that the replication of pGKL plasmids was under the control of the MAT locus. In MATa/MAT alpha cells of S. cerevisiae, the MAT alpha gene product (alpha 2) is combined with the MATa gene product (a1) and the resultant protein, a1-alpha 2, acts to repress the expression of haploid specific genes. Experiments showed that the K. lactis linear plasmids were stably maintained in rho 0 mata1/MAT alpha diploids, indicating that the a1-alpha 2 repressor interfered with the stability of pGKL2. It was revealed by computer analysis that the consensus sequence homologous to the a1-alpha 2 repressor binding site occurred within the coding regions of pGKL2 genes which were presumed to be essential for the plasmid replication. Since the plasmids were stably maintained in diploids of K. lactis, the mating type control must not be working there.
来自乳酸克鲁维酵母的线性杀伤质粒pGKL1和pGKL2，能在酿酒酵母线粒体DNA缺陷型（rho 0）的MATa或MATα单倍体中稳定复制，但在rho 0 MATa/MATα二倍体中不稳定且经常丢失，这表明pGKL质粒的复制受MAT位点控制。在酿酒酵母的MATa/MATα细胞中，MATα基因产物（α2）与MATa基因产物（a1）结合，产生的蛋白质a1-α2可抑制单倍体特异性基因的表达。实验表明，乳酸克鲁维酵母线性质粒能在rho 0 mata1/MATα二倍体中稳定维持，这表明a1-α2阻遏物会干扰pGKL2的稳定性。通过计算机分析发现，与a1-α2阻遏物结合位点同源的共有序列出现在pGKL2基因的编码区内，这些区域被认为对质粒复制至关重要。由于这些质粒能在乳酸克鲁维酵母的二倍体中稳定维持，所以交配型控制在那里必定不起作用。
