Co-introduction of two plasmids with the same CEN element?

[Ashok Aiyar]

I have seen several studies where two ARS/CEN plasmids that share 
the same ARS element but different CEN elements (and selectable
markers) are maintained together in S. cerevisiae.

I have tried to co-introduce two plasmids into the same haploid
strain of S. cerevisiae.  So far I have been unable to select for
transformants that contain both plasmids.  Plating the same
transformations under conditions that select for a marker on one 
plasmid or the other works.

Both these plasmids contain the same CEN element (CEN3).  Obviously
diploid yeast have no problem having two copies of CEN3.  A casual
sequence analysis indicates that all CEN elements have very similar
sequences.

So has anyone else encountered a problem in "co-maintaining" two 
plasmids that contain the same CEN element.  I have just tried to
introduce the two plasmids sequentially into the strain -- and 
should know if that has worked 2 - 3 days.

Thanks,
Ashok




______________O_________oO_____________oO______o_______oO___________________
YEAST bionet newsgroup see: http://www.bio.net/hypermail/YEAST/
YEAST e-mail: messages sent to yeast at net.bio.net
subscribe: e-mail biosci-server at net.bio.net with: subscribe yeast
unsubscribe: e-mail biosci-server at net.bio.net with: unsubscribe yeast
YEAST on the WWW: http://genome-www.stanford.edu/Saccharomyces/VL-yeast.html
problems with the YEAST newsgroup? E-mail the moderator: francis at cmmt.ubc.ca