Distinct domains of IkappaB-alpha inhibit human immunodeficiency virus type 1 replication through NF-kappaB and Rev.
Among the regulators of human immunodeficiency virus (HIV) replication is the cellular transcription factor NF-kappaB, whose activity is regulated through inhibition by IkappaB family members. We have shown previously that I kappaB-alpha inhibits HIV type 1 (HIV-1) replication, and unexpectedly, IkappaB-alpha was found both to suppress HIV-1 transcription and to inhibit Rev function. The relative contributions and specificities of these mechanisms to HIV replication were unknown. Here, we report that the region of IkappaB-alpha which blocks Rev function is separable from that required for inhibition of NF-kappaB. Molecular mutagenesis revealed that the N terminus of IkappaB-alpha is required for inhibition of Rev function, whereas mutants lacking the N terminus retained the ability to inhibit NF-kappaB function. Interestingly, the nuclear export sequence of IkappaB-alpha was not required for inhibition of Rev or NF-kappaB function in mammalian transfection assays. Conversely, the C terminus of IkappaB-alpha was not required for the inhibition of Rev, while deletion of this region resulted in a loss of NF-kappaB inhibition. Another IkappaB family member with a distinct amino-terminal sequence, IkappaB-beta, inhibited NF-kappaB but not Rev function. These studies indicate that the inhibition of Rev by IkappaB-alpha is independent of NF-kappaB. Mutants defective in inhibition of either Rev or NF-kappaB retained the ability to inhibit HIV-1 replication, suggesting that both functions may contribute to the inhibition of HIV replication by I kappaB-alpha.
Wu
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Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0650, USA.
Woffendin
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MacLachlan
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D001665:Binding Sites; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015967:Gene Expression Regulation, Viral; D015694:Gene Products, rev / Q000037:antagonists & inhibitors* / Q000502:physiology; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D020672:I-kappa B Proteins; D019169:Jurkat Cells; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology; D015398:Signal Transduction; D014779:Virus Replication; D054321:rev Gene Products, Human Immunodeficiency Virus
D004268:DNA-Binding Proteins; D015694:Gene Products, rev; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D054321:rev Gene Products, Human Immunodeficiency Virus; D000072000:NF-KappaB Inhibitor alpha