The Autographa californica nuclear polyhedrosis virus immediate-early promoter supplemented with the hr5 enhancer drives expression of EGFP. The coding sequence lacks a poly(A)[+] signal and its 3' end is flanked by an artificial splice donor site. This facilitates the formation of a fusion transcript with a downstream exon of a host gene when PBac{GT1} is inserted into the genome, allowing gene-trapping.