Isolation of Genetic Suppressor Elements (GSEs) from Random Fragment cDNA Libraries in Retroviral Vectors

Cellular phenotypes resulting from decreased function of a specific gene are manifested as recessive, since they are suppressed in the presence of a normal allele of the corresponding gene. The powerful gene-transfer techniques, which have played a key role in the studies of dominant phenotypes, are not readily applicable to recessive traits, since expression of a recessive allele does not generally affect the cellular phenotype. In haploid organisms, random gene disruption can be used as a general method of cloning recessive genes, but this approach is limited to genes that are not essential for cell growth and is not, at least presently, applicable to diploid cells. This explains why studies of recessive genes of higher eukaryotes (e.g., tumor suppressor genes) are in many cases lagging far behind the analysis of dominant genes (e.g., oncogenes).