A full-length Hsp70 promoter drives expression of Su(var)205 which is tagged at the N-terminal end with a ligand-dependent version of Tag:Dam. This consists of the Tag:Dam open reading frame with the 4-hydroxytamoxifen-inducible intein Tag:4-HT-intein inserted just before residue 127 (this residue has been mutated from L to C, since intein splicing requires a C residue downstream of the intein). Insertion of the intein sequence partially inactivates Tag:Dam, but it can be removed by feeding with 4-hydroxytamoxifen to induce intein self-splicing. A Tag:MYC tag has been inserted at the C-terminal end of the Tag:Dam open reading frame.