Methods of expressing an expression product of interest are provided. Accordingly there is provided a method comprising introducing into a cell a polynucleotide comprising an AimR responsive element operatively linked to a nucleic acid sequence encoding the expression product of interest, and contacting said cell with an AimP peptide comprising an amino acid sequence of XXXXGG/A, wherein said AimP peptide is capable of binding said AimR polypeptide and dissociating said AimR polypeptide from said AimR responsive element. Also provided are articles of manufacture, isolated peptides, polynucleotides and nucleic acid constructs.