Table 1 Relative levels of the three viral mRNA classes. The amounts of radioactivy in mRNA signals identified by Northern blotting or by slot blotting experiments (see methods) were measured using a Storm scanner. (A) Relative levels of total intracellular viral RNA were determined as the sum of the radioactivity in the 3 signals corresponding to the 2, 4 and 9 kb mRNAs from the same experiments. Levels are expressed as the percentages of total viral RNA in cells transfected with HIV pNL4.3 only used as a reference (100 %) or with HIV-1 pNL4.3 and an SR plasmid. For the same degree of DNA transfection, the percentages of the unspliced and spliced mRNAs were calculated relative to the total viral RNA considered as 100 %. (B) Values of genomic RNA packaged into a standardized amounts of virions (CAp24 ELISA) are reported relative to the virions produced in the absence of SR protein overexpression (100%).