Expression and function of myc family genes.

The myc family of nuclear oncogenes contains three well-characterized members, c-myc, N-myc, and L-myc. These genes encode related but distinct nuclear proteins that can contribute to tumorigenic conversion both in vitro and in vivo. However, each gene displays a unique activation pattern in spontaneously arising tumors, a pattern that partially reflects the unique expression pattern of each gene during normal development. Although the specific function of myc family genes has not been determined, changes in myc gene expression accompany in vitro exposure to growth and differentiation stimuli, suggesting an important role in these cellular processes. In addition, the homologies shared among myc genes and two groups of DNA binding, transcriptional regulatory proteins suggests a role in regulating gene expression. This review describes the similar and unique properties of individual members of the myc gene family with respect to their expression and potential role during normal development and in the tumorigenic conversion process.