ELUCIDATION OF A CONSERVED RNA STEM-LOOP STRUCTURE IN THE PACKAGING SIGNAL OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

A region of human immunodeficiency virus type 1 (HIV-1) genomic RNA kn own to interact with the viral nucleocapsid protein is one of the cruc ial components for retroviral genomic RNA packaging. We have investiga ted the secondary structure for this RNA packaging signal of HIV-1 usi ng RNA mapping techniques and extensive computer analyses. Our results suggest that the RNA sequence containing the packaging signal conform s to a stable stem-loop structure and that a portion of this structure is conserved among twenty independent HIV-1 isolates. The heterogenei ty of the RNA packaging sequence was not correlated with the amino aci d sequence variability of the viral nucleocapsid protein. These findin gs have critical implication in understanding the viral maturation pro cess.