UASp regulates expression of Arf1 cDNA (LD24904) with the amino acid change I46D that makes its GTPase activity highly insensitive to activation by ASAP1 and weakly insensitive to activation by AGAP1 or Arf GAP1. The shRNA region targeted by P{UASp-Arf1.shRNA2} is mutated (with the encoded protein sequence maintained) to make it resistant to RNAi by P{UASp-Arf1.shRNA2}.