Acts as a transcriptional activator in complex with isoform 2 of meis1, to induce posterior neural and neural crest gene expression, and thereby specify hindbrain and neural crest cell fate. Binds to a highly conserved region in the promoter of the neural crest gene zic3. Required for the nuclear transport or retention of meis1 (By similarity). Forms a heterodimer with meis1; the interaction is necessary for neural fate induction. The displayed sequence corresponds to the ortholog of the mammalian isoform B sequences. There is currently no X.tropicalis ortholog sequence for isoform A. Belongs to the TALE/PBX homeobox family.