c-fos antisense RNA blocks expression of c-fos gene in F9 embryonal carcinoma cells.
To study the function of proto-oncogene c-fos, we prepared an antisense plasmid that expresses in mammalian cells c-fos antisense RNA which is complementary to the endogenous c-fos mRNA. Upon transfection into undifferentiated F9 EC cells, the antisense plasmid directed constitutive expression of a large amount of c-fos antisense RNA. These cells were very low in the basal level of c-fos message and were unable to induce c-fos message when stimulated with interferon or phorbol ester. The failure to induce c-fos message led to the blockade of c-fos protein expression in these cells. Thus, these cells represented a c-fos defective phenotype. The blockade of c-fos gene expression seen in antisense-cells could be caused by rapid degradation of the c-fos message, since c-fos mRNA expression was rescued in these cells when treated with protein synthesis inhibitor, cycloheximide. We found that expression of c-myc gene was down-regulated in c-fos antisense-cells: Although control undifferentiated F9 cells constitutively expressed a high level of c-myc message, the antisense cells had a much lower amount of c-myc mRNA. Since p53 and heat shock gene 70 were expressed at comparable levels in control and antisense cells, c-myc gene expression appears to be regulated by c-fos gene in F9 EC cells. Lastly, these antisense cells grew as rapidly as control F9 cells and underwent differentiation after retinoic acid treatment, indicating that c-fos expression is not a prerequisite for differentiation of F9 cells.
Levi
B Z
BZ
Laboratory of Developmental and Molecular Immunity, National Institute of Child Health and Human Development, Bethesda, MD 20892.
Kasik
J W
JW
Ozato
K
K
D000818:Animals; D002277:Carcinoma; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D010957:Plasmids; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos; D012313:RNA / Q000494:pharmacology*; D018075:RNA, Complementary
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D018075:RNA, Complementary; D012313:RNA; D003513:Cycloheximide