Cell-colony hybridization on a nitrocellulose filter to identify clones expressing a transfected gene

Cells that are transfected with a growth-inhibitory gene can be isolated by using a dominant selective marker. Such isolated clones, however, do not always express the transfected gene. Therefore, clones in which a transfected gene is integrated and expressed should be selected further. We have developed a simple method of identifying such expression-positive clones. We modified the filter hybridization process so that cultured cells are directly transferred to a nitrocellulose filter, immobilized, and hybridized with radiolabeled DNA probes. This method is sensitive enough to detect the presence or the expression of a single-copy gene, and ideal for identifying clones that stably express a transfected gene.