Interleukin 3 (IL-3) induces transcription from nonrearranged T cell receptor γ loci in IL-3-dependent cell lines

The expression of the murine TCR-γ genes was examined in a series of IL-3-dependent and growth factor-independent cell lines. All of the IL-3-dependent cell lines, but none of the IL-3-independent lines, expressed high levels of one or more of the γ genes but did not express the TCR-β genes. None of the cell lines expressing the γ loci contained detectable genomic γ gene rearrangements. Sequencing of cDNA clones from two of the cell lines demonstrated that transcription was from nonrearranged γ loci based on the presence of sequences in the cDNAs that are found immediately 5' of the Jγ4 and Jγ2 genes. The expression of γ transcripts was dependent upon IL-3 and no transcripts were detectable within 6-8 h after the removal of IL-3. Readdition of IL-3, but not granulocyte CSF, resulted in the reappearance of γ transcripts within 30 min. The results demonstrate that IL-3 regulates the expression of nonrearranged γ loci. Since expression is required for rearrangement, it can be hypothesized that IL-3 may influence the ability of lymphoid/myeloid progenitors to commit to the T cell lineage.