Regulation of expression of c-myc protoocogene in a clonal line of mouse lens epithelial cells by serum growth factors.
Steady-state levels of c-myc mRNA were determined in a clonal line of mouse lens epithelial cells in quiescent and growth-stimulated states. Steady-state mRNA levels for c-myc increased rapidly from an undetectable amount in quiescent cells to the maximum level (8-fold) in growth-stimulated cells. In contrast to its steady-state mRNA levels, its rate of transcription increased by only 3.4-fold in serum-stimulated cells versus quiescent cells, indicating that the abundance of c-myc transcripts in lens epithelial cells during the serum-induced transition from quiescence to proliferation is regulated by both transcriptional and post-transcriptional mechanisms. Serum stimulation in combination with cycloheximide caused superinduction in the steady-state levels of c-myc mRNA in lens epithelial cells. These additive increases in c-myc mRNA levels in the presence of cycloheximide could be due to a decrease in the apparent turnover rate of c-myc mRNA, which, in fact, was observed in actively growing cells. DNA synthesis, as revealed by [3H]thymidine uptake, began 18 h after the addition of serum to quiescent cells and peaked at 24 h. From these results it is concluded that the expression of c-myc gene in mouse lens epithelial cells in response to serum induction is growth dependent.
Rao
G N
GN
Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia 30322.
Church
R L
RL
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000032:analysis / Q000096:biosynthesis; D004847:Epithelial Cells; D005786:Gene Expression Regulation / Q000187:drug effects*; D006133:Growth Substances / Q000097:blood / Q000494:pharmacology*; D007908:Lens, Crystalline / Q000166:cytology* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000502:physiology; D016271:Proto-Oncogene Proteins c-myc; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
D006133:Growth Substances; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D012313:RNA; D004247:DNA; D003513:Cycloheximide