[4] Ubx represses selected Dpp (Decapentaplegic-activated) target genes in the anterior and posterior axis.

[5] Several Dpp target genes which have been identified are spalt-related, vestigial, Serum Response Factor, and achaete-scute.

Significant concentrations of Hunchback only exist in the anterior and posterior regions of the embryo, therefore Ubx is expressed only in middle segments.

[7] Activation of Ubx involves multiple cis-acting regulatory sequences, which are found upstream and downstream of the mRNA cap-site.

For example, it has been shown that Ubx expression in the third femur of D. melanogaster is dependent on the enhancer regions abx and pbx.

[8] Transcription factors which bind to the promoter site of Ubx have been purified and shown to activate expression of the gene in vitro.

In addition to requiring less harsh conditions than other proteins, Ubx has been shown to assemble more rapidly and at much lower concentrations.