1. ¹Laboratory of Hematology & Transfusion Medicine, University of Patras, Patras, Greece
2. ²Laboratory of Medical Physics, University of Patras, Patras, Greece
3. ³Laboratory of Microbiology, University of Patras, Patras, Greece
4. ⁴Laboratory of Biological Chemistry, Medical School, University of Patras, Patras, Greece

Correspondence: A Mouzaki, Laboratory of Hematology & Transfusion Medicine, Medical School, University of Patras, Patras GR-26110, Greece. E-mail: mouzaki@med.upatras.gr

Received 14 May 2003; Revised 30 September 2003; Accepted 1 October 2003.

Abstract

Transcriptional repressors controlling the expression of cytokine genes have been implicated in a variety of physiological and pathological phenomena. An unknown repressor that binds to the distal NFAT element of the interleukin-2 (IL-2) gene promoter in naive T-helper lymphocytes has been implicated in autoimmune phenomena and has emerged as a potentially important factor controlling the latency of HIV-1. The aim of this paper was the identification of this repressor. We resorted to public microarray databases looking for DNA-binding proteins that are present in naïve resting T cells but are downregulated when the cells are activated. A Bayesian data mining statistical analysis uncovered 25 candidate factors. Of the 25, NFAT4 and the oncogene ets-2 bind to the common motif AAGGAG found in the HIV-1 LTR and IL-2 probes. Ets-2 binding site contains the three G's that have been shown to be important for binding of the unknown factor; hence, we considered it the likeliest candidate. Electrophoretic mobility shift assays confirmed cross-reactivity between the unknown repressor and anti-ets-2 antibodies, and cotransfection experiments demonstrated the direct involvement of Ets-2 in silencing the IL-2 promoter. Designing experiments for transcription factor analysis using microarrays and Bayesian statistical methodologies provides a novel way toward elucidation of gene control networks.