THE ROLE OF VIRAL ENHANCER CORE MOTIF-RELATED SEQUENCES IN REGULATINGT-CELL RECEPTOR-GAMMA AND RECEPTOR-DELTA GENE-EXPRESSION

T cells express clonally distributed alphabeta or gammadelta Ag recept or heterodimers. Transcriptional enhancers for the genes of all four s ubunits are active in both gammadelta and alphabeta T cells, but are l ess active or inactive in other cells. Conserved sequence motifs are p resent in all four enhancers, suggesting that common transcription fac tors regulate TCR gene expression. One of these motifs in the gamma3 s ite of the TCR-gamma enhancer is similar to motifs found in several ot her lymphoid-specific and viral enhancers. This conserved ''core'' seq uence is present in the enhancers of Moloney and SL3-3 murine leukemia viruses, important for transcription in T cells and in determining di sease specificity. Here we characterize the gamma3 site of the gamma e nhancer and a corresponding homologous site, deltaE3, of the TCR-delta enhancer. Our results suggest that the core site is critical for acti vity of the 200-bp gamma enhancer fragment and of the gamma3 and delta E3 sites. Furthermore, we identify a nuclear factor in human T cell li nes that specifically binds the core region in these and several other core-containing enhancers. This factor may be identical to or related to a purified bovine nuclear core binding factor that binds the core region of the Moloney murine leukemia virus enhancer, gamma3 and delta E3 sites, suggesting that similar proteins regulate the TCR-gamma,delt a and Moloney murine leukemia virus enhancers. Other sequences in the gamma3 site upstream of the core sequence are also critical for activi ty in T cells, suggesting that at least two different factors are requ ired for functional activity of the gamma3 site.