FIGURE 1 The organization and structure of the HIV-1 genomic RNA influences viral protein expression. (a) This portion of the HIV-1 genome shows three open reading frames, gag, pol, and env, that are translated into long polyprotein precursors; proteolytic cleavage generates multiple proteins from each reading frame. Blue bars represent sites that code for interprotein linkers, and yellow bars indicate sites coding for loops between protein domains. Black arrows mark regions of the RNA genome that are highly structured; note that these areas coincide with areas that link proteins or protein domains. (b) An example of RNA secondary structure in the HIV-1 genome.