Figure 2.

Processing of HIV-1 RNA. Outlined in the figure are the cis-acting components of the HIV-1 RNA which control its processing. Indicated are the positions of the 5' splice sites (arrows above the unspliced RNA), 3' splice sites (brackets below the unspliced RNA), and the various ESS and ESE elements that modulate splice site use. At top is an outline of viral genome and on the bottom, the exons which comprise the major spliced forms (4.0 kb singly spliced and 1.8 kb multiply spliced) of the genomic RNA are indicated by black boxes. Multiple spliced RNAs combining or excluding various exons encode each of the viral accessory proteins.