No abstract

Integrase has been implicated in human immunodeficiency virus type 1 (HIV-1) nuclear import. Integrase analyses, however, can be complicated by the pleiotropic nature of mutations: whereas class I mutants are integration defective, class II mutants display additional assembly and/or reverse transcription defects. We previously determined that HIV-1 V165A , originally reported as defective for nuclear import, was a class II mutant. Here we analyzed mutants containing changes in other putative nuclear localization signals, including 186 KRK 188 / 211 KELQKQITK 219 and Cys-130. Previous work established HIV-1 K186Q , HIV-1 Q214L/Q216L , and HIV-1 C130G as replication defective, but phenotypic classification was unclear and nuclear import in nondividing cells was not addressed. Consistent with previous reports, most of the bipartite mutants studied here were replication defective. These mutants as well as HIV-1 V165A synthesized reduced cDNA levels, but a normal fraction of mutant cDNA localized to dividing and nondividing cell nuclei. Somewhat surprisingly, recombinant class II mutant proteins were catalytically active, and class II Vpr-integrase fusion proteins efficiently complemented class I mutant virus. Since a class I Vpr-integrase mutant efficiently complemented class II mutant viruses under conditions in which class II Vpr-integrases failed to function, we conclude that classes I and II define two distinct complementation groups and suggest that class II mutants are primarily defective at a postnuclear entry step of HIV-1 replication. HIV-1 C130G was also defective for reverse transcription, but Vpr-integrase C130G did not efficiently complement class I mutant HIV-1. Since HIV-1 C130A grew like the wild type, we conclude that Cys-130 is not essential for replication and speculate that perturbation of integrase structure contributed to the pleiotropic HIV-1 C130G phenotype.