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plasmids with 2 2 micron circles

Ronan O'Kennedy Ronan.okennedy at ucg.ie
Fri Feb 17 08:19:49 EST 1995

>Are plasmids with more than 1 2micron circles  stable in yeast? I was
>subcloning into pRS424 and some of my miniscreens, in addition to having
>my insert, also have concatamers of pRS424. I transformed them into
>yeast and the gene seems to be expressed but I'm worried about the yeast
>rearranging the plasmids to get rid of the extra 2micron circles.

Hi George,
I don't know of any published studies on this but stability will generally
be a function of copy number of the plasmid. Also will be dependent on the
nature of the plasmid. If the plasmid contains a full 2um sequence it will
be more stable on its own than in a cir+ host. Introduction of another
recombinant full 2um vector will normally  destabilize the first. I'm not
too sure about about 2um fragment based vectors but remember that they will
be more stable in a cir+ and in the presence of a fully active full
2um-sequence vector (such as pJB502 Bijvoet JFM, Vanderzanden AL, Goosen N,
Brouwer J, Vandeputte P (1991). DNA insertions in the silent regions of the
2-=B5m Plasmid of Saccharomyces cerevisiae influence plasmid stability. Yeas=
7 : 347-356.)


Ronan O'Kennedy
Growth and Fermenatation Technology Lab
Dept of Microbiology
University College Galway
Phone ***-91-24411ext 2191
=46ax   ***-91-25700

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