Cotransfection of S. cerevisiae PBN1 and GPI14 cDNAs restored surface expression of CD59 in the mutant cells. CHO2.46 cells (1–4) and Ramos 517-17 cells (5–8) were transiently transfected with cDNAs and analyzed by FACS. 1 and 5, PBN1 cDNA alone; 2 and 6, GPI14 cDNA alone; 3 and 7, PBN1 and GPI14 cDNAs; 4, rat PIG-X cDNA alone; and 8, human PIG-M cDNA alone. Thick lines, transfected cells stained with anti-CD59; dotted lines, nontransfected cells stained with anti-CD59; thin lines in 1–4, CHO F21 cells stained with anti-CD59.