Sequence encoding the core PIKK kinase domain of the protein protein product were floxed by placing a loxP site upstream of exon 57 and floxed neomycin cassette downstream of exon 58. The neomycin cassette was subsequently removed by transient infection of cre recombinase, and exons 57-58 were removed via Cre-mediated recombination in the germline. (J:303736)