FIG. 4.

Levels of unspliced gag mRNA and spliced pol mRNA in the Gag PTC mutants analyzed by RT-PCR assays. (A) PTC mutations are indicated by black lines at the C terminus of Gag. The 5′ss and 3′ss are marked at the 5′ untranslated region of pol. The solid arrow on the right was used to amplify spliced RNA, and the open arrow on the right was used to amplify unspliced RNA in RT-PCR assays. The same reverse primer shown in the solid arrow on the left was used for amplifying both unspliced and spliced mRNAs. (B) 293T cells were transfected with each of the Gag PTC mutant proviruses. Total cellular RNA was isolated and subjected to reverse transcription to make cDNA, and mRNA levels were determined by PCR.