DISTINCT DOMAINS OF I-KAPPA-B-ALPHA INHIBIT HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 REPLICATION THROUGH NF-KAPPA-B AND REV

Among the regulators of human immunodeficiency virus (HIV) replication is the cellular transcription factor NF-kappa B, whose activity is re gulated through inhibition by I kappa B family members, We have shown previously that I kappa B-alpha inhibits HIV type 1 (HIV-1) replicatio n, and unexpectedly, I kappa B-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 I kappa B-alpha which blocks Rev f unction is separable from that required for inhibition of NF-kappa B. Molecular mutagenesis revealed that the N terminus of I kappa B-alpha is required for inhibition of Rev function, whereas mutants lacking th e N terminus retained the ability to inhibit NF-kappa B function, Inte restingly, the nuclear export sequence of I kappa B-alpha was not requ ired for inhibition of Rev or NF-kappa B function in mammalian transfe ction assays. Conversely, the C terminus of I kappa B-alpha was not re quired for the inhibition of Rev, while deletion of this region result ed in a loss of NF-kappa B inhibition, Another I kappa B family member with a distinct amino-terminal sequence, I kappa B-beta, inhibited NF -kappa B but not Rev function. These studies indicate that the inhibit ion of Rev by I kappa B-alpha is independent of NF-kappa B. Mutants de fective in inhibition of either Rev or NF-kappa B retained the ability to inhibit HIV-1 replication, suggesting that both functions may cont ribute to the inhibition of HIV replication by I kappa B-alpha.