A tissue-specific chromatin loop activates the erythroid ankyrin-1 promoter

• Published in: Blood 2012-10, Vol.120 (17), p.3586-3593
• Main Authors: Yocum, Ashley O., Steiner, Laurie A., Seidel, Nancy E., Cline, Amanda P., Rout, Emily D., Lin, Jolinta Y., Wong, Clara, Garrett, Lisa J., Gallagher, Patrick G., Bodine, David M.
• Format: Article
• Language: English
• Subjects: 3' Untranslated Regions; 5' Untranslated Regions; Animals; Ankyrins - genetics; Ankyrins - metabolism; Binding Sites; Biological and medical sciences; Cell Line, Tumor; Chromatin - chemistry; Chromatin - genetics; Chromatin - metabolism; Deoxyribonuclease I - genetics; Deoxyribonuclease I - metabolism; Enhancer Elements, Genetic; Hematologic and hematopoietic diseases; Histones - genetics; Histones - metabolism; Humans; Insulator Elements; K562 Cells; Medical sciences; Mice; Mice, Transgenic; NF-E2 Transcription Factor, p45 Subunit - genetics; NF-E2 Transcription Factor, p45 Subunit - metabolism; Organ Specificity; Promoter Regions, Genetic; Protein Binding; Protein Isoforms - genetics; Protein Isoforms - metabolism; Red Cells, Iron, and Erythropoiesis; Spherocytosis, Hereditary - genetics; Spherocytosis, Hereditary - metabolism
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2012-08-450262

The human ankyrin-1 gene (ANK1) contains 3 tissue-specific alternative promoters. We have shown previously that the erythroid-specific ankyrin 1 (ANK1E) core promoter contains a 5′ DNase I hypersensitive site (HS) with barrier insulator function that prevents gene silencing in vitro and in vivo. Mutations in the ANK1E barrier region lead to decreased ANK1 mRNA levels and hereditary spherocytosis. In this report, we demonstrate a second ANK1E regulatory element located in an adjacent pair of DNase I HS located 5.6 kb 3′ of the ANK1E promoter at the 3′ boundary of an erythroid-specific DNase I–sensitive chromatin domain. The 3′ regulatory element exhibits enhancer activity in vitro and in transgenic mice, and it has the histone modifications associated with an enhancer element. One of the ANK1E 3′HS contains an NF-E2 binding site that is required for enhancer function. We show that a chromatin loop brings the 3′ enhancer and NF-E2 into proximity with the 5′ barrier region including the ANK1E core promoter. These observations demonstrate a model for the tissue-specific activation of alternative promoters that may be applicable to the ∼ 30% of mammalian genes with alternative promoters that exhibit distinct expression patterns.