Functional characterization of the atopy-associated gene PHF11

Background

Polymorphisms in the plant homeodomain finger protein 11 gene (PHF11) are associated with increased total serum IgE levels, asthma, and severe atopic dermatitis (AD) in children. Although PHF11 includes a plant homeodomain, a motif often found in transcriptional regulators, the function of PHF11 has not been investigated.

Objective

We sought to test (1) whether PHF11 regulates the transcription of genes involved in allergic disorders and (2) whether polymorphisms in PHF11 predict changes in the expression or function of this gene.

Methods

Microarray analysis was used to examine the expression of PHF11 in different immune cell subsets, and the function of PHF11 was tested by using small interfering RNA–induced knockdown or overexpression of PHF11 in primary CD4⁺ T cells or Jurkat T cells. Genotype-dependent effects on PHF11 expression were tested by using an allele-specific gene expression, and the transcriptional activity of PHF11 was determined by using luciferase hybrid gene reporter assays and in vitro DNA-binding electromobility shift assays.

Results

PHF11 expression was higher in T_H1 cells relative to that in T_H2 cells, and knockdown of PHF11 expression reduced expression of the T_H1-type cytokines IFN-γ and IL-2. The G-allele of a 3′ untranslated region polymorphism associated with AD was correlated with reduced abundance of PHF11 RNA in T_H1 cells, as well as an increase in a PHF11 isoform lacking exon II. Evidence was also found for a physical and functional interaction between PHF11 and the p65 subunit of nuclear factor κB.

Conclusion

PHF11 is a regulator of T_H1-type cytokine gene expression. The reduction in PHF11 expression seen with an AD-associated genotype could contribute to the strong T_H2 responses that characterize many allergic individuals.

Key words: PHF11, atopic dermatitis, asthma, atopy, T_H1, T_H2, small interfering RNA, nuclear factor κB

Abbreviations used: AD, Atopic dermatitis, HEK, Human embryonic kidney, IL-2R, IL-2 receptor, IL-12R, IL-12 receptor, NF-κB, Nuclear factor κB, NFAT, Nuclear factor of activated T cells, PHD, Plant homeodomain, PHF11, Plant homeodomain finger protein 11, PMA, Phorbol 12-myristate 13-acetate, shRNA, Short hairpin RNA, siRNA, Small interfering RNA, SNP, Single nucleotide polymorphism, UTR, Untranslated region