The present invention relates to methods for targeted insertion of at least one nucleic acid sequence/s of interest into a target genomic locus of a mammalian cell. More specifically, the methods of the invention are based on using nucleic acid cassettes comprising the nucleic acid sequence/s of interest and at least one recognition signal sequence (RSS), for insertion of the nucleic acid sequence of interest into the target genomic locus that is mediated by RAG-catalyzed recombination. The invention further provides cassettes, vectors and vehicles and cells comprising said cassettes, compositions and uses thereof in immunotherapy.
