trp- cold sensitivity

[Robert Reid]

Does anyone know of a cold-sensitive growth phenotype in a trp1-
strain carrying a URA3-marked CEN plasmid.  I have an S288C strain that
is trp1-, his3-, ura3- and leu2-.  I marked chr XV with TRP1 and
mutagenized to find conditional mutants.  I am backcrossing to the same
strain background that is marked with HIS3 at the same locus on chr XV. 
When I check for my phenotype at 26 and 37, I find that most of the trp-
spore products grow very slow at 26 when carrying a URA3-marked CEN
plasmid but they grow fine at 37.  This slow growth is not seen on rich
or synthetic complete media.  It looks like I can suppress this by
adding extra TRP to my URA dropout media, but I would like to know if
anyone has noticed a similar effect.  It would help for future screens.

Thanks for your help ;)

Robert Reid
Thomas Jefferson Univ.