Combinatorial interactions between distinct transcription factors generate
specificity in the controlled expression of target genes. In this report, w
e demonstrated that the HOXB7 homeodomain-containing protein, which plays a
key role in development and differentiation, physically interacted in vitr
o with I kappa B-alpha, an inhibitor of NF-kappa B activity. This interacti
on was mediated by the I kappa B-alpha ankyrin repeats and C-terminal domai
n as well as by the HOXB7 N-terminal domain. In transient transfection expe
riments, I kappa B-alpha markedly increased HOXB7-dependent transcription f
rom a reporter plasmid containing a homeodomain consensus-binding sequence.
This report therefore showed a novel function for I kappa B-alpha, namely
a positive regulation of transcriptional activation by homeodomain-containi
ng proteins.