Establishment and application of both FLP and Cre site-specific recombination systems at the same position in the genome

Both FRT-FRT and LoxP-LoxP sites that are the target sequences of site-specific recombinases have been constructed in a vector,called C4LFY,using the recombinant DNA technique.C4LFY also contains P elements,2 exons and 1 intron of Drosophila yellow gene,yellow promoter and enhancers,and flanking DNA.Since C4LFY made use of two pairs of FRT and LoxP sites,this vector included two site-specific recombination systems.C4LFY was then integrated into Drosophila genome by P-element-mediated germ line transformation.In the presence of the FLP or Cre recombinase,either FLP/FRT or Cre/LoxP recombination reaction was successfully created at the same position in the genome.Using this system,the molecular basis of yellow gene expression and regulation during development have been investigated.Results indicate that the tissue-specific expression of yellow gene is directly regulated by transcriptional enhancers.In addition,the 5' and 3' genomic sequences flanking the yellow gene have been preliminarily studied and their potential role is discussed.