UASt regulatory sequences are fused upstream of a bicistronic transcript that encodes two open reading frames (ORFs) separated by stop codons (the upstream ORF encodes mCherry and is simply present to reduce translation of the Tag:Dam-containing downstream ORF). The downstream ORF ('NanoDam') encodes the VHH(GFP4) nanobody, tagged at the N-terminal end with Tag:Dam.