VIRAL PROTEASE ASSAY BASED ON GAL4 INACTIVATION IS APPLICABLE TO HIGH-THROUGHPUT SCREENING IN MAMMALIAN CELLS

Abstract We present an assay for viral proteases that relies on the proteolytic cleavage of substrate leading to the dissociation of the yeast transcription factor GAL4. A consensus substrate for the cytomegalovirus protease is fused between the DNA binding and transactivating domains of GAL4. Proteolysis inactivates the transcription factor which drives a luciferase reporter system. The assay is performed in mammalian cells, has a robust signal-to-noise ratio, and assesses proteolysis in a physiologic context. A unique feature of the assay is its ability to detect inhibitors of viral replication that act on viral targets other than the protease.