pVALIUM1 allows cloning of a hairpin product downstream of UAS sequences for GAL4-inducible expression; contains v+t1.8 as a selectable marker; contains two introns: a white intron, located between the inverted DNA repeats, and a ftz intron between the hairpin product and the SV40 polyA tail to facilitate hairpin-RNA processing and export from the nucleus; two pentamers of UAS sites, one of which is flanked by loxP sites and can thus be excised using the P1cre recombinase to generate a 5xUAS derivative; an attB sequence to allow phiC31:int-targeted integration at genomic attP landing sites.
Optimization of pVALIUM1, to eventually produce pVALIUM10, is described. The following parameters were tested: the directionality of the hairpin sequences, the choice of the basal promotor, the number and nature of introns, cloning vs. the recombination method, and the presence of insulator sequences.
See TRiP(http://fgr.hms.harvard.edu/trip-plasmid-vector-sets) for downloadable maps, sequences and cloning protocols.
'VALIUM' stands for Vermilion-AttB-Loxp-Intron-UAS-MCS.