Fig. 1.

a Schematic representation of the HIV-1 RNA genome. Cis-acting signals: TAR, transactivation response element; (A)n, poly A; R, repeat sequence, U5, unique 5′ sequence; pbs, primer binding site; DIS, dimer initiation sequence; MSD, major splice donor; cPPT, central polypurine tract; RRE, Rev response element; 3′ PPT, 3′ polypurine tract; U3, unique 3′ sequence. b Proposed secondary structure of cis-acting signals. PAS, primer activation sequence; Ψ, psi, or encapsidation sequence; FS, frameshift sequence