Immunology: guide for a cell-fate decision

Identification of important regulatory region of Th-POK

CD4(+) and CD8(+) T cells develop from CD4(+)CD8(+) thymocytes. Although it has been reported that expression of the transcription factor Th-POK is important for CD4(+) T cell development, the detailed mechanism regulating Th-POK expression is still obscure. By comparing the promoter regions of the Th-POK gene between human and mouse, I found that the region 3600 base pairs (bps) upstream from the transcription initiation site of the Th-POK gene was highly conserved. To identify the important element(s) regulating Th-POK expression in CD4(+) T cells, I investigated the promoter activity of this region using a luciferase assay in the human T cell line Jurkat. I identified a positive regulatory element in this region 22 bps in length located 600 bp upstream from the transcription initiation site. This 22 bp element had a consensus binding sequence for SAP-1, which is encoded by the Elk4 gene and is activated by the Erk pathway. These data suggest that the 22 bp element might positively regulate Th-POK expression through Erk-SAP-1 signaling.