Abstract: Disclosed herein are methods for mutagenizing a mammalian gene, the methods involving introducing into a mammalian cell a retroviral vector which includes a splice acceptor sequence, a transcription termination sequence, and retroviral packaging and integration sequences, the introducing step being carried out under conditions which allow the vector to integrate into the genome of the cell. Also disclosed are retroviral vectors for use in these methods as well as methods for the use of mutagenized cells.

Abstract: The present invention is directed to mutants of the jellyfish Aequorea victoria green fluorescent protein (GFP) having at least 5 and preferably greater than 20 times the specific green fluorescence of the wild type protein. In other embodiments, the invention comprises mutant blue fluorescent proteins (BFPs) that emit an enhanced blue fluorescence. The invention also encompasses the expression of nucleic acids that encode a mutant GFP or BFP in a wide variety of engineered host cells, and the isolation of engineered proteins having increased fluorescent activity. The novel mutants of the present invention allow for a significantly more sensitive detection of fluorescence in engineered host cells than is possible with GFP or with its known mutants.