Molecular cloning and characterization of human ret-II oncogene.

A transformant having ret-II was obtained by transfection of NIH3T3 cells with DNA from a human sigmoid colon cancer. Comparison of the restriction map of ret-II with that of proto-ret revealed that the ret-II has rearrangements both 5' and 3' to the sequence coding for the kinase domain. However, only the upstream rearrangement was consistently observed in all transformants, suggesting that the upstream rearrangement resulted in the activation of proto-ret. The recombination point and replaced sequence of ret-II were different from those previously reported for ret (Takahashi et al., 1985). In addition, ret-II does not retain region coding for transmembrane of proto-ret. This rearrangement, however, was not detected in the original tumor DNA by Southern blot analysis.