Differential expression of four members of the POU family of proteins in activated and phorbol 12-myristate 13-acetate-treated Jurkat T cells.

The POU family of proteins binds specifically to octamer DNA motifs present in the promoters of several genes and regulates their expression. We identified the presence of four members of the POU family of proteins, Oct-1, Oct-2, Oct-T1, and Oct-T2, in the human T-cell line Jurkat. To obtain insight into the physiological role played by these proteins in T cells, we studied the time course of expression of these genes in resting, activated, and phorbol 12-myristate 13-acetate (PMA)-treated cells. The expression of the gene encoding Oct-1 (now assigned the name OTF1 for octamer-binding transcription factor 1) remained unchanged and the levels of Oct-T2 mRNA decreased with increasing time of incubation to undetectable amounts in all three states of T-cell growth. The levels of Oct-2 mRNA and protein were increased in activated cells, were increased to a lesser extent in the PMA-treated cells, and were undetectable in resting cells. The levels of the Oct-T1 transcripts increased dramatically in PMA-treated cells but not in resting or activated cells. Sequence analysis of the Oct-T1 cDNA showed an open reading frame coding for a POU domain-containing protein of 42.7 kDa. Transient transfection of the gene encoding Oct-T1 decreased the activity of the interleukin 2 gene promoter in activated Jurkat cells. Further, there is evidence for an additional octamer-binding protein, Oct-T3, in Jurkat T cells.