5'-REGIONS OF HIV-1 RNAS ARE NOT SUFFICIENT FOR ENCAPSIDATION - IMPLICATIONS FOR THE HIV-1 PACKAGING SIGNAL

The location and nature of the HIV-1 packaging signal are largely unkn own, despite several genetic and biochemical mutational analyses. In t his report we present our attempts to define a minimal HIV-1 packaging signal through the generation of test RNAs containing small blocks of HIV-1 sequences. We constructed RNAs differing in the position and id entity of the HIV-1 sequence and the segments of heterologous sequence s. However, none of the vectors were efficiently encapsidated by wild- type HIV-1 virions. These results contrast those of Moloney murine leu kemia virus and Rous sarcoma virus, where small viral segments mediate the efficient encapsidation of heterologous RNAs. The results suggest that the HIV-1 packaging signal may be extremely dispersed or heavily context-dependent. (C) 1995 Academic Press, Inc.