CD40 ligation and IL-4 use different mechanisms of transcriptional activation of the human lymphotoxin alpha promoter in B cells.
We have previously shown that both CD40 ligation and IL-4 induce lymphotoxin alpha (LT alpha) expression in B cells. We generated a series of truncations of the LT alpha upstream region (-915 to +7 bp) and examined their ability to drive expression of a luciferase (LUC) reporter gene in B cells. The CD40-responsive promoter region of LT alpha was mapped to the region spanning -120 to -52 bp. This region contains an NF-kappa B site (-99 to -89 bp) which was shown to form a complex with nucleoproteins from CD40-stimulated B cells that contained the p50/p65 subunits of NF-kappa B. Mutation of the NF-kappa B site within the -356 to +7 bp region of the LT alpha gene completely abolished its capacity to drive transcription of the LUC gene in response to stimulation with CD40, but not to IL-4. The IL-4-responsive promoter region of LT alpha was mapped to the region spanning -265 to -185 bp. This region contains a site for binding to signal transducers and activators of transcription (STAT) proteins (-197 to -189 bp). This site was shown to form a complex with nucleoproteins from IL-4-stimulated B cells that contained STAT6. Mutation of the STAT site within the -356 to +7 bp region of the LT alpha gene completely abolished its capacity to drive transcription of the LUC gene in response to IL-4, but not to anti-CD40. These results demonstrate that CD40 and IL-4 use distinct mechanisms, namely activation of NF-kappa B and STAT6, respectively, to activate transcription of the LT alpha gene in B cells.
Worm
M M
MM
Division of Immunology, Children's Hospital, Boston, USA.
Tsytsykova
A
A
Geha
R S
RS
D019013:CD40 Antigens / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D015847:Interleukin-4 / Q000502:physiology*; D008233:Lymphotoxin-alpha / Q000235:genetics*; D016328:NF-kappa B / Q000502:physiology; D011401:Promoter Regions, Genetic; D050800:STAT6 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic
D019013:CD40 Antigens; D008233:Lymphotoxin-alpha; D016328:NF-kappa B; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D015534:Trans-Activators; D015847:Interleukin-4