Extensive regions of pol are required for efficient human immunodeficiency virus polyprotein processing and particle...

Human immunodeficiency type 1 particle maturation is dependent upon proteolytic cleavage of the gag and gag-pol precursors by the pol-encoded viral protease. We have investigated the importance of domains of pol other than the protease for particle maturation and gag proteolytic processing. Truncations of the gag-pol polyprotein precursor of HIV-1 were created by deleting segments of the reverse transcriptase coding region or by introducing stop codons in the integrase region of an HIV-1 infectious molecular clone. In these mutants, the protease coding sequence was left intact. Particles produced by all of the mutants displayed abnormal morphologies and impaired proteolytic processing of gag. The severity of particle morphology abnormalities and of gag polyprotein processing impairment appeared to be affected both by the size and by the position of the deletions in pol, suggesting that the integrity of several pol domains within the gag-pol precursor is required for optimal protease activation and particle maturation. Additionally, cotransfection of a deletion mutant with wild-type provirus led to a marked reduction in the titer of infectious virus, suggesting that truncated gag-pol precursors can interfere with wild-type virus assembly and maturation.