METHOD FOR IDENTIFYING CELLULAR GROWTH INHIBITORS

The present invention is a method which permits the selective screening for growth-inhibiting substances having a known mechanism of action; i.e., substances which inhibit or otherwise interfere with an enzyme or other gene product whose function is required for the growth or survival of the cell. T he method employs cells (e.g., bacterial cells) that contain a nucleic acid fragment that encodes an RNA fragment that can interfere with the expression of a gene product (e.g., an anti-sense RNA that hybridizes to a mRNA), where in expression of the RNA fragment pre-sensitizes the cell to substances (drugs) that act at the gene product (e.g., a protein or RNA). The cells lose the capability to express the RNA fragment. In the method, the recombinant cells are grown in a nutrient medium in the presence of a test substance under conditions in which expression of the RNA fragment occurs at a level that pr e- sensitizes the cell to substances that act at the targeted gene product. The growth conditions are also controlled such that the cells lose the capabilit y to express the RNA fragment. When the test substance is a growth inhibitor that acts on the targeted gene product, the cells lacking the RNA fragment (revertant cells) will have a growth advantage over cells containing the RNA fragment, and thegrowth of revertant cells will occur. The method of the invention includes monitoring the cell growth for the appearance of revertan t cells, which leads to the identification of selective growth inhibitors havi ng a specific mode of action.