Epigenetic regulation and nucleosome positioning in the human TATA-less IL-1α promoter

Interleukin-1 alpha (IL-1 alpha) is secreted by a variety of cell types and is a major player in immune and inflammatory processes. Genes involved in immunological processes are known to be strictly regulated; however, how epigenetic mechanisms contribute to this regulation in not understood. To gain insight into the epigenetic regulation of the human TATA-less IL-1A gene, we show that active and silent chromatin modifications characterize the regulatory regions of IL-1 alpha in expressing and non-expressing cells, respectively, and that the DNA methylation in the proximal promoter is associated with the expression status of the cells. Interestingly, although nucleosome depletion in active promoters is found in yeast and fly genes, now it has been reported in human promoters. We here show on the level of single DNA molecules that in expressing cells, a nucleosome is absent in about half of the proximal IL-1 alpha promoters. This observation might reflect a more subtle regulation of nucleosome positioning in TATA-less genes or human genes in general.