Figure 1. Overview of the HIV-1 viral life cycle and the mRNAs produced. A. Following entry into the host cell, the viral RNA is reverse-transcribed into a viral cDNA intermediate which is integrated into the host cell genome. The DNA is transcribed and the resulting pre-mRNA is processed into over 30 different RNA species. The resultant viral RNAs are translated into a subset of viral proteins and the full-length RNA is packaged into new virions. B. Diagram of the 5′ leaders from the transcripts encoding for gag, vif, vpr, vpu and nef, displaying splicing patterns, leader length, and IRES activity relative to B-globin 5′ UTR.¹⁴ Blue depicts the common 289 nt region present on the 5′ end of all the transcripts.