Determination of transrepression domains of the human N-myc protein.

: The myc gene family, including c- and N-myc, is believed to play a critical role in the regulation of cell cycle and proliferation. The function of N-myc, in contrast to c-myc, is not clearly understood. Here we report that, using a N-myc expression vector in CAT and S1 nuclease protection assays, the N-myc protein trans-represses expression of the human N-myc, the mouse N-myc, and the human MHC class 1 antigen genes. The analysis of N-myc deletion mutants showed that the N-terminal region where there are amino acid sequences highly conserved in the myc family and the central region where the acidic amino acids are concentrated, are necessary for trans-repression activity. Also, the region near the C-terminus is relevant for DNA-protein and protein-protein interaction; in particular, the basic region, helix-loop-helix, and leucine zipper are important for activity.