cDNA library screening using the SOS recruitment system

The SOS recruitment system (SRS), a recently developed method for detecting protein-protein interactions, provides an attractive alternative to identi fy biologically important protein interactions. In SRS, the protein-protein interactions rake place in the cytoplasm instead of the nucleus, as is the case in the conventional two-hybrid system. Athough the SRS has overcome s ome of the disadvantages of the conventional two-hybrid system, it still ha s several problems and limitations. Here, we describe a new protocol for SR S library screening. A new combination of growth media to avoid the tedious step of replica plating greatly increases the number of independent coloni es irt a single library screening. Furthermore, we designed a pair of ms-sp ecific primers and a one-step simple PCR to rule out the must abundant fals e positive, the mammalian ras cDNA, in SRS library screening.