IGF-I increases c-fos expression in FRTL5 rat thyroid cells by activating the c-fos promoter.
We studied the effect of IGF-1 on c-fos mRNA expression in FRTL5 rat thyroid cells. IFG-1, or calf serum, transiently increased c-fos mRNA levels in quiescent FRTL5 cells, with the latter being more potent. This increase was prevented by actinomycin D. FRTL5 cells were stably transfected with the c-fos promoter linked upstream to the reporter gene chloramphenicol acetyl transferase (CAT). Calf serum and IGF-1 increased c-fos promoter activity in a prolonged manner, and to an equal degree. Our data indicate that IGF-1, as well as additional factor(s) in serum, increase c-fos mRNA levels, at least in part, by activation of the c-fos promoter.
Damante
G
G
Department of Medicine, Veterans' Administration Medical Center, San Francisco, California 94121.
Cox
F
F
Rapoport
B
B
D000818:Animals; D001769:Blood; D002478:Cells, Cultured; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009857:Oncogenes; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D013002:Somatomedins / Q000494:pharmacology*; D013936:Thymidine / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D013936:Thymidine