KAPPA-B ENHANCER-BINDING COMPLEXES THAT DO NOT CONTAIN NF-KAPPA-B AREDEVELOPMENTALLY-REGULATED IN MAMMALIAN BRAIN

DNA-binding complexes which are temporally regulated in developing rat brain have been identified by their ability to interact with the kapp aB enhancer sequence in electrophoretic mobility-shift assays. These c omplexes, referred to as developing-brain factors (DBFs) 1 and 2, are abundant in nuclear extracts from developing rat brain through postnat al day 2 and decline to nearly undetectable levels by postnatal day 7. DBFs were not detected in extracts from cultured cell lines or in tis sues other than the developing brain. The highest level of DBF DNA-bin ding activity was observed in developing cortex, and the lowest in cer ebellum. In UV crosslinking experiments, a labeled kappaB oligonucleot ide probe crosslinked 110- and 115-kDa proteins from DBF complexes. DB Fs are likely to be involved in the regulation of transcriptional even ts which take place during brain development.