Rapid Screening Assay for Revertants derived from MSV-transformed Cells

Abstract

MURINE sarcoma virus (MSV)-transformed 3T3FL cells (S⁺L⁻ cells¹) produced spontaneously and at variable rates flat variants (revertants) from which MSV could no longer be rescued by superinfection with murine leukaemia virus (MuLV)^2,3. During the course of investigation of reversion frequency in S⁺L⁻ cells, we have been able to detect revertants by a rapid screening assay technique instead of using the more cumbersome cloning procedure in microtitre wells as previously described^2,3. The S⁺L⁻ cell line 3197^1–3 was composed of hyper-refractile, loosely attached cells and did not form a compact cell monolayer. Infection of this cell line with MuLV changed the cellular morphology to a slightly more rounded cell type, and increased the tendency of cells to detach readily from the surface of the container. When rescue-negative revertants derived from S⁺L⁻ cells were infected with MuLV there was no observable change in cellular morphology. These characteristics can be used as the basis for a rapid screening assay technique for revertants from S⁺L⁻ cells, the details of which are described here.