The kappaB sites in the human immunodeficiency virus type 1 long terminal repeat enhance virus replication yet are not absolutely required for viral growth.
The dependence of human immunodeficiency virus type 1 (HIV-1) on its NF-kappaB binding sites (kappaB sites) for replication in transformed and primary T-cell targets was examined by infecting cells with HIV-1 reporter viruses containing kappaB site enhancer mutations. Viral transcription was measured either with luciferase-expressing HIV-1 that infects for a single round or by flow cytometric analyses with HIV-1 expressing placental alkaline phosphatase (PLAP) or green-fluorescent protein (GFP). Both PLAP- and GFP-expressing viruses spread from cell to cell and allowed analysis of viral gene expression patterns in single cells. Infection of a panel of T-cell lines with different basal levels of NF-kappaB demonstrated a direct correlation between the amount of constitutive nuclear NF-kappaB and the degree to which a wild-type virus outperformed kappaB site mutants. One T-cell line with a constitutively high level of nuclear NF-kappaB, PM1, showed a 20-fold decrease in transcription when its kappaB sites were mutated. In contrast, in a T-cell line with a low basal level of NF-kappaB, SupT1, mutation of the kappaB site in the enhancer had no effect on viral transcription or growth rate. Phytohemagglutinin-activated peripheral blood mononuclear cells showed a large dependence on the kappaB sites for optimal virus growth. Viruses without marker genes corroborated the finding that mutations to the kappaB sites impair virus production in cells with a high basal level of NF-kappaB. These data show that in T cells, HIV-1 can use NF-kappaB to enhance its growth but the virus is clearly able to grow in its absence.
Chen
B K
BK
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Feinberg
M B
MB
Baltimore
D
D
D001483:Base Sequence; D004279:DNA, Viral; D016655:HIV Core Protein p24 / Q000032:analysis; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014779:Virus Replication
D004279:DNA, Viral; D016655:HIV Core Protein p24; D016328:NF-kappa B