Dual Luciferase assay
We measured the knockdown of firefly luciferase using the Promega Dual Luciferase Reporter Assay. Here, Renilla luciferase is used for normalization. The measurements were conducted on the Promega GLOMAX 96 Microplate Luminometer using the Promega standard protocol.
Twenty hours after transfection, cells were washed with 1x PBS and lysed using 1x Passive Lysis Buffer (5x stock solution diluted with distilled water), shaking for 30 minutes at 37°C. 10µl of the lysate were transferred to a white microplate (LumaPlate) as required for Luminometer measurements.
LAR II reagent was prepared by resuspending Luciferase Assay Substrate in 10ml Luciferase Assay Buffer II. For Stop & Glo reagent, 2.1ml 50x Stop & Glo substrate and 105ml Stop & Glo Buffer were added to the amber Stop & Glo reagent bottle and mixed by vortexing. Reagents where stored in 15ml aliquots at -80°C and thawed freshly prior to each measurement.
To set up the Luminometer, the two injectors where flushed with distilled water, 70% ethanol, again water and air, three times each. Afterwards, they were primed three times with substrate reagents.
The activity of the first luciferase (firefly) was measured by adding 25µl of LAR II reagent to the well. The enzyme reacts upon translation without further processing and oxidates beetle luciferin, resulting in photon emission that can be measured. In addition to beetle luciferin, the LAR II reagent contains coenzyme A, which accelerates the reaction and thus creates a prolonged luminescence signal. The luminescence was measured two seconds after addition of the reagent, for ten seconds. Afterwards, 25µl Stop & Glo reagent was added, which is able to quench the firefly luciferase activity and simultaneously contains the substrate for Renilla luciferase, coelenterazine. This second reaction also emits photons upon oxidation of the substrate. Addition of substrates and light emission measurements were conducted automatically by the GLOMAX Luminometer.
References
Bruce A. Sherf, Shauna L. Navarro,Rita R. Hannah and Keith V. Dua l-LuciferaseTM Reporter Assay: An Advanced Co-Reporter Technology Integrating Firefly and Renilla Luciferase Assays. WoodPromega Notes Magazine Number 57, 1996, p.02
Consumables and Reagents
LumaPlate, PerkinElmer, catalogue number 6005630
Promega Dual-Luciferase® Reporter Assay System, catalogue number E1910
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