Lesion-induced increase in nerve growth factor mRNA is mediated by c-fos.
Lesion of the sciatic nerve caused a rapid increase in c-fos and c-jun mRNA that was followed about 2 hr later by an increase in nerve growth factor (NGF) mRNA. To evaluate whether the initial increase in c-fos mRNA is causally related to the subsequent increase in NGF mRNA, we performed experiments with fibroblasts of transgenic mice carrying an exogenous c-fos gene under the control of a metallothionein promoter. In primary cultures of these fibroblasts, CdCl2 evoked a rapid increase in exogenous c-fos mRNA, followed immediately by an increase in endogenous c-jun mRNA and with a slight delay by an increase in NGF mRNA. In fibroblasts of C3H control mice, CdCl2 had no effect on the mRNA levels of the protooncogenes c-fos and c-jun or of NGF. Additional evidence for a causal relationship between c-fos induction and the subsequent increase in NGF mRNA was obtained in cotransfection experiments. Fibroblasts of C3H control mice were cotransfected with a metallothionein-promoter-driven c-fos expression vector and a NGF promoter-chloramphenicol acetyltransferase reporter gene construct. Induction of the exogenous c-fos by CdCl2 resulted in increased activity of the NGF promoter. DNase I footprint experiments demonstrated that a binding site for transcription factor AP-1 (Fos/Jun heterodimer) in the first intron of the NGF gene was protected following c-fos induction. That this protected AP-1 site indeed was functional in the regulation of NGF expression was verified by deletion experiments and by a point mutation in the corresponding AP-1 binding region in the NGF promoter-chloramphenicol acetyltransferase reporter construct.
Hengerer
B
B
Max Planck Institute for Psychiatry, Department of Neurochemistry, Martinsried/Munich, Federal Republic of Germany.
Lindholm
D
D
Heumann
R
R
Rüther
U
U
Wagner
E F
EF
Thoenen
H
H
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics*; D003850:Deoxyribonuclease I; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D008668:Metallothionein / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D009414:Nerve Growth Factors / Q000235:genetics*; D015345:Oligonucleotide Probes; D009924:Organ Culture Techniques; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D012584:Sciatic Nerve / Q000378:metabolism*; D012867:Skin / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D004268:DNA-Binding Proteins; D009414:Nerve Growth Factors; D015345:Oligonucleotide Probes; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D014157:Transcription Factors; D008668:Metallothionein; D011505:Protein-Tyrosine Kinases; D003850:Deoxyribonuclease I