Preferential expression of the novel alternative isoform I.3 of hypoxia-inducible factor lot in activated human T lymphocytes

Hypoxia-inducible factor-1 alpha (HIF-1 alpha) is critical not only in the regulation of oxygen homeostasis but also in the regulation of innate and adaptive immune systems. We previously reported that T-cell receptor-mediated activation of T cells in mice leads to the expression of an. alternative isoform of HIF-1 alpha that inhibits activated T cells in a delayed negative feed-back manner. In this paper, we describe a novel mRNA isoform of human HIF-1 alpha that is upregulated in peripheral T lymphocytes after T-cell receptor stimulation. This activation-inducible isoform is expressed using the alternative first exon I.3, and it encodes a protein that is 24 amino acids Longer than the ubiquitous HIF-1 alpha isoform. This mRNA isoform I.3 of HIF-1 alpha is expressed in a tissue-specific manner with the highest expression found in peripheral blood leukocytes and the thymus. (C) 2008 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.