DEFECTIVE TRANSFER RNA-QUEUINE MODIFICATION IN C3H10T1 2 MURINE FIBROBLASTS TRANSFECTED WITH ONCOGENIC RAS/

tRNA isoacceptors for aspartic acid, asparagine, histidine, and tyrosi ne are modified in the anticodon wobble position with the deazaguanine analogue queuine, Queuine modification is defective in many tumors an d transformed cell lines, and the extent of hypomodification correlate s with staging and outcome in numerous human tumors. The molecular rol e of queuine modification in normal cells and the mechanism of queuine hypomodification in tumors are unknown, We have characterized non-tra nsformed C3H10T1/2 murine fibroblasts (C3H) and their ras-transfected counterparts (RasC4) with respect to the causes and effects of queuine hypomodification, RasC4 cells are hypomodified for queuine compared w ith C3H cells, despite increased tRNA-guanine ribosyltransferase activ ity, Excess exogenous queuine can cause repletion of tRNA queuine leve ls in RasC4 cells. Queuine modification of both C3H and RasC4 cells ca n be decreased by treatment with 7-methylguanine. This treatment does not affect growth in monolayer culture but enhances anchorage-independ ent growth of RasC4 cells greatly. These cell lines may be useful syst ems for the study of queuine function in normal cells and the causes a nd consequences of hypomodification for queuine in tumors.