National Institute of Biomedical Genomics, P.O.:N.S.S., Kalyani, West Bengal 741251, India.
National Institute of Biomedical Genomics, P.O.:N.S.S., Kalyani, West Bengal 741251, India.
Cytokine. 2021 Jun;142:155491. doi: 10.1016/j.cyto.2021.155491. Epub 2021 Mar 13.
Interferon lambda 3 (IFN-λ3 or IFNL3, formerly IL28B), a type III interferon, modulates immune responses during infection/inflammation. Several human studies have reported an association of single nucleotide polymorphisms (SNP) in the IFNL3 locus with expression level of IFNL3. Previous genetic studies, in the context of hepatitis C virus infections, had predicted three regulatory SNPs: rs4803219, rs28416813 and rs4803217 that could have functional/causal roles. Subsequent studies confirmed this prediction for rs28416813 and rs4803217. A dinucleotide TA-repeat variant (rs72258881) has also been reported to be regulating the IFN-λ3 promoter. In this study, we tested all these genetic variants using a sensitive reporter assay. We show that the minor/ancestral alleles of both rs28416813 and rs4803217, together have a strong inhibitory effect on reporter gene expression. We also show an interaction between the two principal transcription factors regulating IFNL3 promoter: IRF7 and NF-kB RelA/p65. We show that IRF7 and p65 physically interact with each other. By using a transient ChIP assay, we show that presence of p65 increases the promoter occupancy of IRF7, thereby leading to synergistic activation of the IFNL3 promoter. We reason that, in contrast to p65, a unique nature of IRF7 binding to its specific DNA sequence makes it more sensitive to changes in DNA phasing. As a result, we see that IRF7, but not p65-mediated transcriptional activity is affected by the phase changes introduced by the TA-repeat polymorphism. Overall, we see that three genetic variants: rs28416813, rs4803217 and rs72258881 could have functional roles in controlling IFNL3 gene expression.
干扰素 lambda 3（IFN-λ3 或 IFNL3，以前称为 IL28B）是一种 III 型干扰素，可调节感染/炎症期间的免疫反应。几项人类研究报告称，IFNL3 基因座中的单核苷酸多态性（SNP）与 IFNL3 的表达水平有关。先前的遗传研究在丙型肝炎病毒感染的背景下预测了三个调节 SNP：rs4803219、rs28416813 和 rs4803217，它们可能具有功能/因果作用。随后的研究证实了 rs28416813 和 rs4803217 的这一预测。据报道，二核苷酸 TA 重复变异（rs72258881）也可调节 IFN-λ3 启动子。在这项研究中，我们使用灵敏的报告基因检测所有这些遗传变异。我们表明，rs28416813 和 rs4803217 的次要/祖先等位基因共同对报告基因表达具有强烈的抑制作用。我们还展示了调节 IFNL3 启动子的两个主要转录因子 IRF7 和 NF-kB RelA/p65 之间的相互作用。我们表明，IRF7 和 p65 相互物理作用。通过使用瞬时 ChIP 测定，我们表明 p65 的存在增加了 IRF7 的启动子占有率，从而导致 IFNL3 启动子的协同激活。我们推断，与 p65 相比，IRF7 与其特定 DNA 序列的结合的独特性质使其对 DNA 相位变化更加敏感。结果，我们看到 IRF7 而不是 p65 介导的转录活性受到 TA 重复多态性引入的相位变化的影响。总的来说，我们看到三个遗传变异：rs28416813、rs4803217 和 rs72258881 可能在控制 IFNL3 基因表达方面具有功能作用。
