Constitutive expression of c-fos antisense RNA blocks c-fos gene induction by interferon and by phorbol ester and reduces c-myc expression in F9 embryonal carcinoma cells.
To address the role of c-fos proto-oncogene we constructed a plasmid that allows constitutive expression of RNA complementary to c-fos mRNA, and stably introduced this plasmid into F9 embryonal carcinoma cells. Some F9 clones expressing c-fos antisense RNA had a reduced basal level of c-fos mRNA, and were unable to induce a c-fos mRNA as well as its protein when stimulated with phorbol ester or with interferon (IFN). Nevertheless, the ability to induce major histocompatibility class I genes following IFN treatment was not impaired in these clones. Clones expressing c-fos antisense RNA grew as rapidly as control F9 cells, and underwent differentiation after retinoic acid treatment. Unexpectedly, constitutive expression of c-myc mRNA was reduced on average by 10-fold in clones expressing c-fos antisense RNA. However, expression of the p53 gene and heat shock gene hsp 70 was not affected in these clones, indicating the existence of a specific regulatory linkage between c-fos and c-myc genes. Cycloheximide treatment led to induction of a large amount of c-fos mRNA in clones expressing c-fos antisense RNA as well as in control F9 clones. The amount of c-fos antisense RNA was also increased by cycloheximide treatment. We postulate that c-fos antisense RNA blocks expression of the endogenous c-fos gene by accelerating the degradation of c-fos mRNA and that cycloheximide treatment interferes with this degradation.
Levi
B Z
BZ
Laboratory of Developmental and Molecular Immunity, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Ozato
K
K
D002454:Cell Differentiation; D002461:Cell Line, Transformed; D002999:Clone Cells; D003513:Cycloheximide / Q000494:pharmacology; D005452:Fluoresceins; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D006801:Humans; D007372:Interferons / Q000494:pharmacology*; D009693:Nucleic Acid Hybridization; D010703:Phorbol Esters / Q000494:pharmacology*; D010957:Plasmids; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000235:genetics*; D015533:Transcriptional Activation; D014212:Tretinoin / Q000494:pharmacology
D005452:Fluoresceins; C000715470:MAS1 protein, human; D010703:Phorbol Esters; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D014212:Tretinoin; D007372:Interferons; D003513:Cycloheximide