The Human myc Gene Family

The myc family of cellular oncogenes contains three well-defined members, c-myc, N-myc, and L-myc. The first-identified and most thoroughly studied member of this family, c-myc, was identified as the cellular homolog to the transforming gene of an avian retrovirus. The c-myc gene encodes a nuclear protein that appears to be involved in the growth and division of a wide variety of normal cells, and deregulated expression of the c-myc gene has been implicated as contributory to the development of numerous classes of tumors. Such deregulated expression occurs by a number of mechanisms, including viral transduction, promoter (enhancer) insertion, translocation, and gene amplification (for review, see Varmus 1984). Although the precise function of the c-myc gene has not been elucidated, it is generally thought that the c-myc protein mediates a signal associated with cell division and, thus, regulation of its expression is required for normal cell growth.