UASt regulatory sequences drive expression of smo containing the amino acid replacement R580Q (the equivalent mutation in the human ortholog results in an oncogenic protein that is associated with basal cell carcinoma). The Tag:ER(KKDE) sequence has been added to the C-terminal end of the open reading frame, to localize the protein to the endoplasmic reticulum (the first "K" is part of the normal smo sequence, so three amino acids were added). In addition, a GFP tag has been inserted after the signal peptide sequence (after residue Ser 33).