Transcriptional activity of the gibbon ape leukemia virus in the interleukin 2 gene of MLA 144 cells.

The gibbon ape leukemia virus (GALV)-infected T-cell line, MLA 144, constitutively makes the lymphokine, interleukin 2 (IL 2), without stimulation by antigen or mitogen. This line contains two GALV insertions in the IL-2 gene: one in the 3' untranslated region of the gene and one 1200 bp 5' to the gene. It is likely that one or both of these viral insertions is(are) involved in activation of IL-2 expression. We investigated the ability of sequences within the LTR of MLA 144 cells (GALV-MLA) to act as transcriptional elements and have demonstrated here the presence of cis-acting sequences in the GALV LTR capable of enhancing transcription of the GALV promoter as well as two heterologous promoters, SV40 early and IL-2. The results indicate that insertion of the enhancer element(s) alone is not sufficient to activate IL-2 expression but can enhance levels of IL-2 expressed from the activated gene.