Identification of c-fos sequences involved in induction by insulin and phorbol esters.
We evaluated the mechanism of insulin and phorbol ester induction of the proto-oncogene c-fos in Chinese hamster ovary fibroblasts stably transformed with high levels of genes expressing normal or truncated human insulin receptors. Both insulin and the tumor-promoting phorbol ester phorbol 12-myristate 13-acetate (PMA) induced c-fos mRNA accumulation in cells expressing high numbers of normal human insulin receptors; PMA but not insulin was effective in the cells expressing the mutant receptor. Transient expression studies with plasmid constructions containing c-fos 5'-flanking sequences ligated to the bacterial chloramphenicol acetyltransferase gene indicated that sequences corresponding to the serum response element were required for induction of c-fos transcription by both insulin and PMA. The insulin-sensitive cells contained a nuclear factor, presumably a protein, which bound specifically to this sequence of the c-fos gene; the apparent affinity of this factor to the normal serum response element was not affected by prior treatment of the cells with insulin or PMA. This c-fos binding factor may prove to be important in the regulation of c-fos expression by insulin and activators of protein kinase C.
Stumpo
D J
DJ
Howard Hughes Medical Institute Laboratories, Durham, North Carolina 27710.
Stewart
T N
TN
Gilman
M Z
MZ
Blackshear
P J
PJ
D000123:Acetyltransferases / Q000235:genetics; D001483:Base Sequence; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D010703:Phorbol Esters / Q000494:pharmacology*; D010957:Plasmids; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000096:biosynthesis; D011972:Receptor, Insulin / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
D007328:Insulin; C000715470:MAS1 protein, human; D010703:Phorbol Esters; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D000123:Acetyltransferases; D015500:Chloramphenicol O-Acetyltransferase; D011972:Receptor, Insulin; D013755:Tetradecanoylphorbol Acetate