cDNA cloning of mRNAS which increase rapidly in human lymphocytes cultured with concanavalin-A and cycloheximide

To induce or "superexpress" genes involved in the entry of cultured GO lymphocytes into the G1-phase of the cell cycle, the cells were treated for 2 hours with a lectin (concanavalin-A) and a protein synthesis inhibitor (cycloheximide). A cDNA library was generated from small quantities of RNA by the high efficiency method of Gubler & Hoffman (1). 30,000 colonies were screened for differential hybridization to cDNA corresponding to treated cultures, but not to cDNA corresponding to control cultures. 50 recombinants were identified on this basis. One recombinant (#7) corresponded to mRNA (2150 base pairs) which was increased by cycloheximide alone, but was not increased by concanavalin A. Another recombinant (#19) corresponded to 2 mRNAs (980 and 1120 base pairs) one or both of which were increased either by concanavalin-A or by cycloheximide. It is speculated that the latter mRNAs are products of a locus which is activated when the concentration of a repressor is decreased by concanavalin-A or cycloheximide.