Isolation of the CD7 gene from the DNA of transfected L cells

Using DNA from L cells which expressed high levels of the CD7 (Leu-9 or HuLy-m2) antigen obtained after two cycles of transfection, a genomic library was constructed in the lambda phage Charon 4A. Recombinant clones containing the gene coding for this antigen were identified by first screening the library with both the HSV-tk gene and a probe detecting the human repetitive (Alu) sequences. DNA from 10 tk+ and 12 Alu+ recombinant clones was used to transfect L cells which were analyzed for the cell-surface expression of CD7 either early (48-72 h posttransfection) or later when hypoxanthine aminopterin thymidine-resistant colonies were obtained. Transfection with either Alu+ or tk+ recombinant phages led to transient early expression of CD7, and stable CD7+ transfectants were also established. Thus the CD7 gene has been isolated in a number of clones in association with either the Alu repetitive sequence or with the HSV-tk gene; the insert size in one of the genomic clones was 13.5 kb.