Bianchi M M, Santarelli R, Frontali L
Department of Cell and Developmental Biology, University of Rome La Sapienza, Italy.
Curr Genet. 1991 Mar;19(3):155-61. doi: 10.1007/BF00336481.
Plasmid factors involved in the stable propagation of pKD1-derived vectors in Kluyveromyces lactis transformants have been identified. Three genes (A, B and C) have been found to be present in pKD1: the interruption of the B and C genes led to high plasmid instability. Stability could be restored in trans when host cells contained pKD1 as the resident plasmid (pKD1+ strains). The A gene, which codes for a site-specific recombinase, did not affect plasmid partitioning. Vectors bearing only the pKD1 replication origin (or a chromosomal ARS), and no other pKD1 sequence, were very unstable both in the presence and absence of the resident plasmid in host cells. These vectors could be stabilized in pKD1+ strains, but not in pKD1 degree strains, by the insertion of a 200 bp-long pKD1 sequence. This sequence, called the cis-acting stability locus (CSL), together with the products of the B and C genes, ensured plasmid partitioning at cell division. Possible hairpin structures and direct repeats were regularly spaced within the CSL. This region, and the corresponding cis-acting stabilizing elements of other yeast plasmids, did not have sequence homology but shared some structural regularities.
已鉴定出参与pKD1衍生载体在乳酸克鲁维酵母转化子中稳定增殖的质粒因子。已发现pKD1中存在三个基因（A、B和C）：B和C基因的中断导致质粒高度不稳定。当宿主细胞含有pKD1作为常驻质粒（pKD1+菌株）时，可通过反式作用恢复稳定性。编码位点特异性重组酶的A基因不影响质粒分配。仅携带pKD1复制起点（或染色体ARS）而无其他pKD1序列的载体，在宿主细胞中无论有无常驻质粒都非常不稳定。通过插入一段200 bp长的pKD1序列，这些载体可在pKD1+菌株中稳定，但在pKD1°菌株中则不能。该序列称为顺式作用稳定位点（CSL），与B和C基因的产物一起，确保了细胞分裂时的质粒分配。CSL内可能的发夹结构和直接重复序列规则排列。该区域以及其他酵母质粒相应的顺式作用稳定元件没有序列同源性，但具有一些结构规律。
