The present invention relates to a method for regulating gene expression, comprising introducing into a cell each of a recombinant vector which expresses a first domain comprising N-terminus of a Cas9 protein, and a recombinant vector which expresses a second domain comprising C-terminus of a Cas9 protein, a composition comprising the recombinant vectors, a kit for regulating gene expression, and a method for intracellular production of Cas9 protein. Moreover, the present invention relates to a transformed cell introduced with a viral vector which packages the first domain, and a viral vector which packages the second domain, and to a composition comprising a virus produced therefrom.