The psiCHECK™-1 Vector and psiCHECK™-2 Vector provide a quantitative and rapid approach to optimize RNA interference (RNAi). The vectors enable monitoring of changes in expression of a target gene fused to the reporter gene. In both vectors,Renillaluciferase is used as a primary reporter gene, and the gene of interest can be cloned into the multiple cloning region located downstream of theRenillatranslational stop codon. Initiation of the RNAi process towards a gene of interest results in cleavage and subsequent degradation of fusion mRNA. Measurement of decreasedRenillaluciferase activity is a convenient indicator of RNAi effect.