A common single nucleotide polymorphism in the CD14 promoter decreases the affinity of Sp protein binding and enhances transcriptional activity.
CD14 is a pattern recognition receptor that plays a central role in innate immunity through recognition of bacterial lipoglycans, primarily LPS. Recently, our group has identified a common single nucleotide polymorphism, -159C-->T, in the CD14 proximal promoter. Homozygous carriers of the T allele have a significant increase in soluble CD14, but a decreased total serum IgE. This epidemiologic evidence led us to investigate the molecular basis for the effects of CD14/-159C-->T on CD14 regulation in monocytes and hepatocytes, the two major cell types known to express this gene in vivo. EMSA analysis showed that the T allele results in decreased affinity of DNA/protein interactions at a GC box that contains a binding site for Sp1, Sp2, and Sp3 transcription factors. In reporter assays, the transcriptional activity of the T allele was increased in monocytic Mono Mac 6 cells, which express low levels of Sp3, a member of the Sp family with inhibitory potential relative to activating Sp1 and Sp2. By contrast, both alleles were transcribed equivalently in Sp3-rich hepatocytic HepG2 cells. Our data indicate that the interplay between CD14 promoter affinity and the [Sp3]:[Sp1 + Sp2] ratio plays a critical mechanistic role in regulating transcription of the two CD14 alleles. Variation in a key gene of innate immunity may be important for the pathogenesis of allergy and inflammatory disease through gene-by-gene and/or gene-by-environment interactions.
LeVan
T D
TD
Arizona Respiratory Center, University of Arizona, Tucson, AZ 85724, USA. Tricia.LeVan@resp-sci.arizona.edu
Bloom
J W
JW
Bailey
T J
TJ
Karp
C L
CL
Halonen
M
M
Martinez
F D
FD
Vercelli
D
D
D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020862:GC Rich Sequence; D017930:Genes, Reporter; D006367:HeLa Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000235:genetics*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D051704:Sp2 Transcription Factor; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D018950:Lipopolysaccharide Receptors; C497119:SP2 protein, human; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051704:Sp2 Transcription Factor; D051705:Sp3 Transcription Factor