Plays a role in posterior cephalic patterning. Probable subunit of a heterodimeric regulatory protein involved in the control of head morphogenesis. Isoform B may have a repressive effect on Dfd response elements, thereby modifying the activity and specificity of the Hox system and moving the body anterior/posterior axis. Embryonic expression of isoform B is localized to the mandibular segment and the hypopharyngeal and labral primordia first detectable in late blastoderm stages. Embryonic expression of isoforms B and C is ubiquitous. Isoforms A and C are maternally and zygotically expressed in embryos. Isoform A reduced between 2-12 hours embryos and then increases. Isoform B is expressed in later embryonic stages. Isoform C has the lowest expression level of the isoforms. Belongs to the bZIP family. CNC subfamily. Contaminating sequence. Potential poly-A sequence. Extended N-terminus.