The role of Sp1 and NF-kappa B in regulating CD40 gene expression.
CD40 is a member of the tumor necrosis factor receptor superfamily and is a key signaling molecule expressed by antigen-presenting cells of the immune system. In a previous paper, we demonstrated that the expression of CD40 is regulated by both post-transcriptional and post-translational processes. In this paper, we show that basal (constitutive) CD40 gene expression is regulated by a TATA-less promoter, with Sp1 as a key transcription factor. Two Sp1 binding regions were identified in the mouse CD40 promoter at positions -59 to -50 and -74 to -66. Surprisingly, Sp1-mediated CD40 transcription was reduced following lipopolysaccharide stimulation and was associated with a time-dependent reduction in Sp1 DNA binding activity. This reduction seemed to be mediated by phosphorylation of the Sp1 molecule. We also show here that CD40 expression in lipopolysaccharide-stimulated cells is up-regulated by NF-kappaB through two distinct sites. One of these sites (-128 to -119) was shown to bind p50 and p65 members of the NF-kappaB family, while the other site (-562 to -553) bound only p65. Transfectants of p65 were generated using RAW 264 cells, and it was shown that the up-regulation of CD40 mRNA expression was dependent on the presence of the p65 molecule.
Tone
Masahide
M
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom. mtone@molbiol.ox.ac.uk
Tone
Yukiko
Y
Babik
Jennifer M
JM
Lin
Chun-Yen
CY
Waldmann
Herman
H
D001483:Base Sequence; D019013:CD40 Antigens / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D005786:Gene Expression Regulation; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000502:physiology*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D016329:Sp1 Transcription Factor / Q000502:physiology*; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic
D019013:CD40 Antigens; D004268:DNA-Binding Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D004247:DNA