20xUAS regulatory sequences drive expression of a mutated form of lin-28 (carries mutations in the CSD domain which convert the amino acids at positions 45, 54 and 65 to Ala residues and carries mutations in the CCHC domain that converts amino acids at positions 136 and 158 to Ala residues) which is tagged at the C-terminal end with three copies of Tag:FLAG and then three copies of Tag:HA.