title: Plasmid functions involved in the stable propagation of the pKD1 circular plasmid in Kluyveromyces lactis.
abstract: 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.
authors.affiliation: Department of Cell and Developmental Biology, University of Rome La Sapienza, Italy.
authors.forename: M M
authors.initials: MM
authors.lastname: Bianchi
authors.forename: R
authors.initials: R
authors.lastname: Santarelli
authors.forename: L
authors.initials: L
authors.lastname: Frontali
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D004254:DNA Nucleotidyltransferases / Q000235:genetics; D004261:DNA Replication; D005798:Genes, Bacterial; D005822:Genetic Vectors; D019426:Integrases; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids; D045522:Recombinases; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014170:Transformation, Genetic
chemical_list: D045522:Recombinases; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C115006:integron integrase IntI1