A functional NF-kappaB enhancer element in the first intron contributes to the control of c-fos transcription.
Eukaryotic gene transcription is controlled not only by gene promoters but also by intragenic cis-elements. Such regulation is important for the transcription of immediate early genes (IEGs) and in particular for the c-fos gene, the first intron of which contains many potential transcription factor binding elements. In the present study, we addressed the intronic control of c-fos transcription by the NF-kappaB signalling pathway in the neuroendocrine cell line GH4C1. Tumour necrosis factor alpha (TNFalpha) activating the NF-kappaB signalling pathway induced transcription of the c-fos gene and enhanced thyrotropin-releasing hormone-stimulated (TRH-stimulated) c-fos transcription. To examine the effects of NF-kappaB, the presumed NF-kappaB binding sequence in the first intron was mutated or deleted from c-fos reporter gene constructs. When GH4C1 cells transfected with the reporter constructs were stimulated by TNFalpha, the induced expression was significantly diminished. Double-stranded short DNA with the intronic NF-kappaB binding consensus sequence interacted directly with NF-kappaB p50 protein in vitro; mutation of 3 nucleotides destroying the consensus abolished the in vitro interaction. The importance of NF-kappaB for c-fos expression was also supported by RNA interference experiments; knock-down of NF-kappaB p50 suppressed TNFalpha-induced c-fos expression. In addition, chromatin immunoprecipitation indicated that NF-kappaB occupied the first intron of the c-fos gene in vivo. In conclusion, NF-kappaB enhances c-fos transcription via the direct binding to a response element situated in the first intron.
Charital
Ysadora Maisonnasse
YM
Fondation pour Recherches Médicales, University of Geneva, 64 av. de la Roseraie, 1211 Geneva, Switzerland.
van Haasteren
Goedele
G
Massiha
Abbas
A
Schlegel
Werner
W
Fujita
Toshitsugu
T
D000818:Animals; D001483:Base Sequence; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D007438:Introns / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D016328:NF-kappa B; D016760:Proto-Oncogene Proteins c-fos; D014409:Tumor Necrosis Factor-alpha; D013973:Thyrotropin-Releasing Hormone