Analysis of the transforming potential of the human homolog of mos.

The human homolog, c-moshu, of the mouse cellular mos proto-oncogene (c-mosmu) transforms NIH 3T3 cells at low efficiency. Furthermore, the c-moshu-induced foci are less distinct, and transformed cells contain a high level of human mos protein. The transforming activity of hybrid mos genes derived from human and mouse sequences reveals three domains within the coding region, as well as a negative regulatory sequence upstream from the c-moshu ORF that reduces its transforming efficiency. The mos C-terminal region, however, which contains the src-kinase homology domain, appears to have the greatest influence on transforming efficiency. The low transforming efficiency of c-moshu may provide a selective advantage to the host, but it also may indicate a reduced or modified function of mos in humans.