Title: HLA-C Level Is Regulated by a Polymorphic Oct1 Binding Site in the HLA-C Promoter Region
Authors: Vince N, Li H, Ramsuran V, Naranbhai V, Duh FM, Fairfax BP, Saleh B, Knight JC, Anderson SK, Carrington M.
Journal: Am J Hum Genet,99(6):1353-1358 (2016)
Differential HLA-C levels influence several human diseases, but the mechanisms responsible are incompletely characterized. Using a validated prediction algorithm, we imputed HLA-C cell surface levels in 228 individuals from the 1000 Genomes dataset.
We tested 68,726 SNPs within the MHC for association with HLA-C level. The HLA-C promoter region variant, rs2395471, 800 bp upstream of the transcription start site, gave the most significant association with HLA-C levels (p = 4.2 x 10-66). This imputed expression quantitative trait locus, termed impeQTL, was also shown to associate with HLA-C expression in a genome-wide association study of 273 donors in which HLA-C mRNA expression levels were determined by quantitative PCR (qPCR) (p = 1.8 x 10-20) and in two cohorts where HLA-C cell surface levels were determined directly by flow cytometry (n = 369 combined, p < 10-15).
rs2395471 is located in an Oct1 transcription factor consensus binding site motif where the A allele is predicted to have higher affinity for Oct1 than the G allele. Mobility shift electrophoresis demonstrated that Oct1 binds to both alleles in vitro, but decreased HLA-C promoter activity was observed in a luciferase reporter assay for rs2395471_G relative to rs2395471_A on a fixed promoter background. The rs2395471 variant accounts for up to 36% of the explained variation of HLA-C level.
These data strengthen our understanding of HLA-C transcriptional regulation and provide a basis for understanding the potential consequences of manipulating HLA-C levels therapeutically.
Citation: Vince N, Li H, Ramsuran V, Naranbhai V, Duh FM, Fairfax BP, Saleh B, Knight JC, Anderson SK, Carrington M. HLA-C Level Is Regulated by a Polymorphic Oct1 Binding Site in the HLA-C Promoter Region Am J Hum Genet,99(6):1353-1358 (2016).