On 25 Mar 1997 14:22:50 GMT, lichten at helix.nih.gov (Michael Lichten)
>In article <espinoza.859230092 at cgl.ucsf.edu>, espinoza at cgl.ucsf.edu>(Hernan Espinoza) wrote:
>>> Albert Spielmann <Albert.spielmann at bota.unine.ch> writes:
>>>> >I'm working with the two-hybrid system from Clontech.
>> >The yeast strains are CG1945 and Y190. Both have a ura3-52 deletion.
>> >Normally they can't grow without uracil. But as said in the supplier's
>> >protocol, it must grow!! Why?
>>>> Your question is a bit ambiguous, under what conditions must the
>> strains grow? I'm not familiar with the Clonetech system, but I would
>> wager it's to select for a URA3 marker on a plasmid...
>>Let's clear up a misconception right now. ura3-52 is NOT a deletion; it's
>a Ty insertion in the URA3 coding region.
>lichten at helix.nih.gov
The yeast strain Y190 DOES carry the ura3-52 marker at the ura3 locus.
However this strain is URA+ because it contains a WT URA3 gene which
was used as a marker to insert the GAL->lacZ sequence. This sequence
is composed of the GAL promoter linked to the E. coli lacZ coding
sequence. It is used as a color stain to determine when the GAL
promoter has been activated by a two hybrid interaction.