THE RECEPTOR-RECYCLING AND LYSOSOME BIOGENESIS MUTANT TFT1.11 BELONGSTO A NEW COMPLEMENTATION GROUP, END6

We have previously isolated a Chinese hamster ovary (CHO) mutant with a temperature-dependent pleiotropic defect in receptor recycling. This mutant, TfT1.11, has also been shown to have defects in fluid-phase e ndocytosis and lysosome biogenesis. Previously isolated CHO cell mutan ts with defects in endocytosis have been assigned to five recessive co mplementation groups (End1-End5). We have performed complementation an alysis using polyethylene glycol-induced fusion of genetically marked sublines of TfT1.11 with representative mutants from each of the End g roups. Complementation of the receptor trapping and lysosome biogenesi s defects as well as temperature lethality was observed with all group s, demonstrating that TfT1.11 defines a new complementation group, End 6.