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A new system for amplifying 2 μm plasmid copy number in Saccharomyces cerevisiae
Author(s) -
Unternährer S.,
Pridmore D.,
Hinnen A.
Publication year - 1991
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1991.tb00801.x
Subject(s) - plasmid , biology , saccharomyces cerevisiae , genetics , yeast , gene , autonomously replicating sequence , microbiology and biotechnology , origin of replication
Summary The yeast 2 μm plasmid is found in the nucleus of almost all Saccharomyces cerevisiae strains. Its replication is very similar to that of chromosomal DNA. Although the plasmid does not encode essential genes it is stably maintained in the yeast population and exhibits only a small, though detectable, loss rate. This stability is achieved by a plasmid‐encoded copy‐number control system which ensures constant plasmid levels. For the investigation of 2μm replication, a yeast strain that is absolutely dependent on this plasmid was constructed. This was achieved by disruption of the chromosomal CDC9 gene, coding for DNA ligase and providing this essential gene on a 2μm‐derived plasmid. This plasmid is absolutely stable under all growth conditions tested. Using the temperature‐sensitive mutant allele cdc9 ‐1 we have developed an artificial control system which allows one to change the copy number of 2μm‐derived plasmids solely by changing the incubation temperature.