Acts as a transcriptional repressor of the GATA3 promoter. Sequence-specific DNA-binding factor that binds to the 5'-AGGTCTC-3' sequence within the negative cis-acting element intronic regulatory region (IRR) of the GATA3 gene (By similarity). Induces thymocyte apoptosis when overexpressed, which may indicate a role in regulation of thymocyte homeostasis.