GATA-3 DOMINANT-NEGATIVE MUTANT - FUNCTIONAL REDUNDANCY OF THE T-CELLRECEPTOR-ALPHA AND RECEPTOR-BETA ENHANCERS

The GATA family of transcription factors regulates a wide variety of g enes, including those involved in differentiation of erythrocytes and T lymphocytes. We report here the creation of a dominant negative muta nt of GATA-3, KRR, which effectively blocks wild-type GATA-1, GATA-2, and GATA-3 transactivation when coexpressed in transient assays. KRR w as generated by site-directed mutagenesis while investigating a putati ve activation domain of GATA-3, located between its two zinc fingers. The GATA-3 KRR mutation does not affect expression, nuclear translocat ion, or the ability to bind to a consensus GATA sequence. KRR can supp ress the activity of the minimal T cell receptor (TCR) alpha and beta enhancers by 12- and 3.4-fold, respectively. However, KRR did not have a significant effect on the activity of larger TCR-alpha and -beta en hancer fragments. Thus, functional redundancy in the TCR-alpha and -be ta enhancers can compensate for the loss of GATA-3 activity.