IFNL1 gene promoter single nucleotide polymorphism rs7247086 enhances transcription through a STAT-binding site.

A single nucleotide polymorphism (SNP) within the human interferon lambda 1 (IFN-L1, IFN-λ1) gene promoter, rs7247086 (C/T) has been reported to be associated with severe dengue and possibly with psoriasis and COVID-19. However, its functional nature is unknown. The present study was undertaken to examine the effect of rs7247086 on transcription, by utilizing promoter and enhancer-reporter assays. We see that the T allele completes a consensus signal transducer and activator of transcription (STAT)-binding site. While we did not find strong evidence to show that the STAT-binding site drove transcription from the IFNL1 gene promoter, we saw that it acts like an enhancer in reporter assays. The T allele of rs7247086 within the STAT-binding site significantly increased transcription of the reporter gene compared to the C allele when incorporated into enhancer-reporter constructs in both HEK293 and A549 cell lines. Mechanistically, we obtained evidence from electrophoretic mobility shift assays to show that the T allele binds to STAT proteins more strongly than the C allele. In a cohort of healthy individuals, we saw that the T allele carriers, specifically males but not females, had significantly increased secretion of IFN-λ1 from their peripheral blood mononuclear cells after stimulation. Lastly, rs7247086 significantly associated with psoriasis, only in males but not in females.