Abstract: The invention provides a site-specific modification method of a DNA molecule that enables gene function manipulation. In particular, the invention provides a method for manipulating gene function by a site-specific action on a target DNA molecule, said method comprising a step for preparing a complex containing an Argonaute protein, a guide RNA and an additional sequence and a step for contacting the target DNA molecule with the complex, wherein the guide RNA is designed to guide the complex to a region containing the desired site in the target DNA molecule.

Abstract: The invention provides a miniaturized cytidine deaminase-containing complex for modifying DNA formed by combining a nucleic acid sequence recognition module and cytidine deaminase, wherein the nucleic acid sequence recognition module specifically binds to a target nucleotide sequence of double-stranded DNA, the cytidine deaminase is composed of an amino acid sequence composed of a region of amino acid residues at positions 30-150 of SEQ ID NO: 1, an ortholog thereof, an amino acid sequence having mutations of one or several amino acids therein, or an amino acid sequence having at least 90% similarity thereto, and the targeted site of the double-stranded DNA is modified.