L-myc Cooperates with ras to Transform Primary Rat Embryo Fibroblasts

Abstract

Recent molecular analysis has revealed that L-myc has several domains of extremely conserved amino acid sequence homology with c-myc and N-myc, suggesting similarity of function. We tested the biologic activity of L-myc by using an expression vector containing a cDNA clone coding for the major open reading frame in the 3.9-kilobase mRNA of L-myc under the control of a strong promoter (Moloney long terminal repeat) and found that L-myc complemented an activated ras gene in transforming primary rat embryo fibroblasts. However, the efficiency of transformation was 1 to 10% of that seen with the c-myc and simian virus 40 (SV40) controls. The L-myc/ras transformants initially grew more slowly than c-myc or SV40 transformants, but once established as continuous cell lines, they were indistinguishable from cell lines derived from c-myc/ras or SV40/ras transfectants as determined by morphology, soft-agar cloning, and tumorigenicity in nude mice.

A Transfected L-myc Gene Can Substitute for c-myc in Blocking Murine Erythroleukemia Differentiation

“…These data show that a transfected L-mnvc gene expressed at a constant level during HMBA induction can block the differentiation of MEL cells. This result demonstrates another biologic activity that L-rnyc shares with c-mnvc in addition to the previously identified transforming activity (1,6). Of interest, L-mvchas been reported to have weak transforming activity in comparison with c-mvc, but.…”