A method of suppressing the expression of a selected endogenous gene in a eukaryotic cell the method comprising introducing into the cell (a) a polypeptide comprising a nucleic acid binding portion which binds to a site at or associated with the selected gene and a modifying portion which comprises a polypeptide or peptidomimetic which is capable of modulating covalent modification of nucleic acid or chromatin, for example a chromatin inactivation portion, or (b) a polynucleotide encoding said polypeptide. The binding of the molecule to nucleic acid may be modulated by a ligand and the molecule may comprise a ligand binding portion. The nucleic acid binding portion may be a nucleic acid binding portion of a nuclear receptor DNA binding protein.
