Inhibition of PC-12 cell differentiation by the immediate early gene fra-1.
The rat pheochromocytoma cell line (PC-12) offers a powerful in vitro model to study the mechanism of growth factor-induced differentiation and proliferation. Within minutes of addition, agents such as nerve growth factor (NGF), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and dibutyryl cyclic AMP (db cAMP) rapidly activate cellular immediate early genes such as c-fos, c-jun, jun-B, and egr-1. fra-1, a member of the immediate early gene family, follows a distinctly later time course of induction than c-fos, c-jun, jun-B, and egr-1, suggesting that fra-1 may attenuate the action of genes induced earlier. We demonstrate that constitutive expression of fra-1 in PC-12 cells results in pronounced inhibition of NGF-induced differentiation. Transcriptional activation of c-fos, c-jun, jun-B, and egr-1 by NGF, EGF, and db cAMP was down-regulated to a varying extent whereas NGF-induced ornithine decarboxylase (ODC) was not affected. Expression of jun-D was not affected in PC-12 fra-1 cells. Transfection of fos and egr-1 promoter-chloramphenicol acetyl transferase (CAT) plasmid into these stable fra-1-expressing PC-12 cells revealed that repression of fos and egr-1 was exerted at the promoter level. Thus deregulated fra-1 expression may inhibit PC-12 cell differentiation by altering the patterns of immediate early gene expression.
Ito
E
E
Department of Molecular Genetics, Hoffmann-La Roche, Inc., Nutley, NJ 07110.
Sweterlitsch
L A
LA
Tran
P B
PB
Rauscher
F J
FJ
Narayanan
R
R
D000310:Adrenal Gland Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics / Q000473:pathology*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D051766:Early Growth Response Protein 1; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017874:Immediate-Early Proteins; D009414:Nerve Growth Factors / Q000494:pharmacology; D010673:Pheochromocytoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D011401:Promoter Regions, Genetic / Q000235:genetics* / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000473:pathology
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D009414:Nerve Growth Factors; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D004815:Epidermal Growth Factor; D003994:Bucladesine