Identification of two novel negative regulatory elements in the tcrα gene

The expression of the T cell receptor α (TCRα) gene is controlled at different levels by positive and negative mechanisms. One approach to further elucidate the regulatory circuits that operate in repression of gene expression is that of somatic cell hybrids. We have generated T x fibroblast somatic cell hybrids in which the expression of the TCRα gene was repressed to various degrees. These hybrids harbor the previously identified silencer activity and there is an apparent inverse correlation between the level of TCRa mRNA versus the levels of the silencer activity. Interestingly, we have identified two novel negative regulatory elements which are located 3' to the TCRα enhancer. Moreover, the introduction of point mutations within these sequences severely compromises their silencing ability. The repression conferred by these novel silencers is active in fibroblast and in T x fibroblast somatic cell hybrids, but is inactive in T-cells. We suggest that multiple silencers are likely to play an important role in establishing tissue-specific TCRα gene expression.