Overexpression of mCAT1 in the producer cell impairs F-MLV infectivity. (A) Expression of Slc7a1 mRNA (encoding mCAT1) in M. dunni cells, 293T cells, and 293 cells stably transfected with murine Slc7a1 (293-mCAT1 cells) relative to that of murine Hprt or human HPRT mRNA in M. dunni and 293 cells, respectively. Shown are the means ± SEMs (n = 3). (B) Frequency of F-MLV-infected (glyco-Gag-positive) M. dunni, B-3T3, or N-3T3 cells 3 days after infection with the indicated doses of FB29 or FB29-DM viruses produced by transfection of 293-mCAT1 cells. The results of one representative of three experiments conducted are shown.