Promoterless Renilla luciferase vectors are designed primarily to accept a putative promoter element for investigation of important regions controlling gene transcription. Alternatively, they may be used as promoterless control vectors in a dual-reporter system with a firefly luciferase vector serving as the experimental vector. The promoterless vectors are available with three varieties of engineered Renilla luciferase genes: hRluc, hRlucP or hRlucCP. The hRluc gene is engineered to remove most cryptic transcription factor binding sites and improve mammalian expression through codon optimization. The hRlucP and hRlucCP and RapidResponse genes are hRluc genes appended with degradation sequences to influence the cellular half-life of the hRluc gene. The RapidResponse genes respond more rapidly to stimuli but at the expense of signal intensity. The hRlucP gene responds more rapidly than hRluc2 with moderate signal intensity, and the hRlucCP responds more quickly with the lowest signal intensity. The promoterless pGL4.82[hRluc/Puro], pGL4.83[hRlucP/Puro] and pGL4.84[hRlucCP/Puro] Vectors are available with the selectable marker puromycin.