Abstract: Provided is a composition for simultaneously targeting a nucleic acid sequence and providing intron selection in cells in vitro, ex vivo or in vivo. The composition includes one or more nucleic acid molecules each including an artificial nucleic acid sequence flanked with capping sequences, and Lambda beta protein or a linear or circular vector including a nucleic acid sequence encoding the Lambda beta protein, wherein each of the capping sequences is homologous to a region in a target nucleic acid sequence, and the artificial nucleic acid sequence is an intron sequence. The present disclosure also provides a method for editing a target nucleic acid sequence in cells by introducing the composition into the cells.