BRN-3.0 - A POU-DOMAIN PROTEIN EXPRESSED IN THE SENSORY, IMMUNE, AND ENDOCRINE SYSTEMS THAT FUNCTIONS ON ELEMENTS DISTINCT FROM KNOWN OCTAMER MOTIFS

Characterization of Brn-3.0 and identification of a highly related mem ber (Brn-3.1) of the class IV POU-domain family suggest potential role s of Brn-3.0 in the development of retinal ganglion cells and sensory neurons, as well as potential roles in the pituitary gland and the imm une system. Brn-3.0 is expressed in the pituitary gland and in a corti cotroph cell line. A functional DNA response element has been identifi ed in the proopiomelanocortin promoter. In contrast to previously desc ribed mammalian POU-domain proteins, Brn-3.0 binds relatively ineffect ively to known octamer DNA motifs, but instead binds with high affinit y to a distinct set of DNA elements, functioning as a transcriptional activator. Brn-3.0, Brn-3.1, and the Drosophila tI-POU share an N-term inal region of homology, referred to as the ''POU-IV box,'' which is s imilar to a conserved functional domain in the c-myc gene family.