FIG. 5.

Exon 5E isoforms do not have greater stability than exon 4bE isoforms. (A) HeLa cells were transfected with env cDNA plasmids with or without pLTRrev1, and 24 h later, cells were either treated (+) or untreated (−) with actinomycin D (Act-D) for a further 0, 4, 8, and 12 h prior to RNA harvesting. Five micrograms of RNA per sample was analyzed for native env mRNA via RPA using RNase A-RNase T1 digestion and autoradiography. Molecular sizes in nucleotides are shown on the left. (B) Densitometry analysis of protected bands (untreated cells, ▪; treated cells, ▴). P, undigested probe; R, probe plus RNase; M, mock (no env or pLTRrev1); Rev, pLTRrev1; E1R and E2R, plasmids expressing env1 and env2 R38 mutant isoforms; E1, pDRenv1. Density equals photostimulated luminescence minus background.