Identification of the C-terminal activation domain of the NeuroD-related factor (NDRF)

Neuron-related factor (NDRF) is a basic helix-loop-helix (bHLH) protein who se expression is restricted to the central nervous system, and is considere d to be responsible for maintenance of differentiated neurons as well as ne urogenesis. NDRF structurally resembles NeuroD in the bHLH region and can i nduce neurogenesis ectopically in ectodermal cells of the Xenopus embryo. I n this study, we delineated the functional domains of NDRF. Using GAL4/NDRF fusion proteins, we identified the C-terminal activation domain (C-AD) in NDRF between amino acid positions 294 and 383. This region was highly homol ogous to one part of the activation domain of NeuroD. We further investigat ed the transactivational function of C-AD in the mouse type 1 inositol 1,4, 5-trisphosphate receptor promoter, which has an NDRF site. Truncation of C- AD resulted in reduction of the activation function, whereas the DNA-bindin g specificity was not affected. These results suggest that C-AD has a stimu latory function in the mammalian nervous system.