| Abstract: | DNA from the human myeloid cell line HL-60 was cotransfected with the cloned thymidine kinase (tk) gene of herpes simplex virus into tk-deficient mouse L cells. tk-positive recipients expressing antigens detected on HL-60 cells were isolated with a fluorescence-activated cell sorter by use of a panel of monoclonal antibodies that detect epitopes on both normal and malignant myeloid cells. Independently sorted populations of transformed mouse cells showed concordant reactivities with four of the monoclonal antibodies in the panel (DU-HL60-4, MY7, MCS.2, and SJ-D1), which suggested that these antibodies reacted to products of a single human gene. A second round of DNA transfection and cell sorting was performed with donor DNA from primary transformants. Two different dominant selection systems were used to isolate secondary mouse L cell and NIH/3T3 cell transformants that coexpressed the same epitopes. Analysis of cellular DNA from secondary mouse cell subclones with a probe specific for human repetitive DNA sequences revealed a minimal human DNA complement containing a characteristic set of restriction fragments common to independently derived subclones. Two glycoproteins, of 130,000 (gp130) and 150,000 (gp150) mol wt, were specifically immunoprecipitated from metabolically labeled lysates of mouse cell transformants and were shown to contain [35S]methionine-labeled tryptic peptides identical to those of analogous glycoproteins expressed in the donor human myeloid cell line. Kinetic and biochemical analyses established that gp130 is a precursor that differs in its carbohydrate moiety from gp150, the mature form of the glycoprotein detected on the cell surface. The isolation of human gene sequences encoding gp150 in a mouse cell genetic background provides the possibility of molecularly cloning the gene and represents a general strategy for isolating human genes encoding differentiation-specific cell surface antigens. |
