To integrate plasmids into the ura3 locus we always linearize them with
NcoI. However, we use strains with the ura3-52 mutation (a Ty insertion).
I don't know the kind of mutation in your ura3-1 allel. You might have
problems if it is a deletion mutation.
Dr. Eckhard Boles
Email: boles at bio1.bio.th-darmstadt.de