title: Regulation of expression of c-fos and c-myc in rat lymphoma Nb-2 cells.
abstract: This study examined the effects of the mitogen, prolactin and the cell cycle inhibitors, cyclosporin A and neomycin sulfate, on expression of the proto-oncogenes c-fos and c-myc in the rat lymphoma Nb-2 cell line. Stimulation of quiescent cultures with prolactin resulted in a 2-3-fold increase in the constitutive levels of c-myc mRNA which peaked at 4 h and declined thereafter. c-Fos mRNA was not detected in quiescent or prolactin-stimulated cultures. Cyclosporin A or neomycin sulfate reversibly blocked the mitogenic effect of prolactin on Nb-2 cells, but had little effect on constitutive levels of c-myc. However, the release of Nb-2 cells from a cyclosporin A or a neomycin sulfate block resulted in a rapid transient induction of c-fos which peaked at 0.5-1 h and declined rapidly thereafter. These results indicate that the rapid transient expression of c-fos following release from cell cycle blockage was not sufficient to elicit cell division, but these cells were competent to respond to prolactin. Prolactin allows progression through the cell cycle and enhances c-myc mRNA levels.
mesh_terms: D000818:Animals; D002460:Cell Line; D003524:Cyclosporins / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007399:Interphase; D008223:Lymphoma / Q000235:genetics*; D009355:Neomycin / Q000494:pharmacology; D009857:Oncogenes; D011388:Prolactin / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats
chemical_list: D003524:Cyclosporins; D012333:RNA, Messenger; D011388:Prolactin; D009355:Neomycin