Western blot analysis of cell-type dependent expression of HIV-1 proteins. HeLa-tat III, 293T and COS7 cells were transfected as described above with mutant and wild type proviral DNA constructs. Forty-eight hrs post-transfection, cells were washed and harvested in 1× RIPA buffer. Denatured cell lysates were then resolved by SDS-PAGE, transferred to a nitrocellulose membrane and immunoblotted with a pool of two HIV-1 positive sera (A), rabbit anti-cyclophilin A (B), and anti-calnexin (C) antibodies. Positions of specific viral and cellular proteins are indicated on the right.