FACT mutants are lethal with an sds3 mutation or RCO1 overexpression. (A) Tenfold dilutions of strains DY150 (wild type), DY8107 (spt16-11), DY2413 (sds3), and DY10482 (spt16-11 sds3) were plated on complete medium for 2 days at either 25°C or 30°C. (B) Tenfold dilutions of strains DY150 (wild type), DY7378 [pob3(L78R)], DY2413 (sds3), and DY10507 [pob3(L78R) sds3] with a YCp-URA3-POB3 plasmid were plated on either complete or FOA-containing medium for 3 days at 20°C. (C) Strains DY150 (wild type), DY7379 [pob3(L78R)], and DY8107 (spt16-11) were transformed with the indicated multicopy plasmid, and 10-fold dilutions were plated on selective medium lacking uracil for 4 days at 20°C or 26.5°C or for 2 days at 30°C or 33°C.