Nitric oxide inhibits HIV tat-induced NF-kappaB activation.
To evaluate the roles of nitric oxide (NO) on human immunodeficiency virus (HIV) Tat-induced transactivation of HIV long terminal repeat (HIV-LTR), we examined the effect of NO in the regulation of nuclear factor (NF)-kappaB, a key transcription factor involved in HIV gene expression and viral replication. In the present study, we demonstrate that HIV Tat activates NF-kappaB and that this activation can be attenuated by endogenous or exogenous NO. Inhibition of endogenous NO production with the NO synthase (NOS) inhibitor L-NMMA causes a significant increase in Tat-induced NF-kappaB activity. In addition, NO attenuates signal-initiated degradation of IkappaBalpha, an intracellular inhibitor of NF-kappaB, and blocks the DNA binding activity of the NF-kappaB p50/p50 homodimer and p50/p65 heterodimer. To determine how NO is induced by HIV Tat, reverse transcription polymerase chain reaction was used to demonstrate the induction of NOS-2 and NOS-3 mRNA by Tat. Although a putative NF-kappaB binding site was identified in the -74 GGAGAGCCCCC -64 region of the NOS-3 gene promoter, gel mobility shift assays and site-directed mutation analyses suggest that the putative NF-kappaB site is not of primary importance. Rather, several Sp-1 sites adjoining the putative NF-kappaB binding site in the promoter region of NOS-3 gene are required for the induction of NOS-3 gene expression by Tat.
Chen
F
F
Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, West Virginia University, Morgantown, USA.
Lu
Y
Y
Castranova
V
V
Rojanasakul
Y
Y
Miyahara
K
K
Shizuta
Y
Y
Vallyathan
V
V
Shi
X
X
Demers
L M
LM
D000818:Animals; D001483:Base Sequence / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D015696:Gene Products, tat / Q000502:physiology; D016325:HIV Long Terminal Repeat / Q000235:genetics; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology; D015533:Transcriptional Activation / Q000502:physiology
D015696:Gene Products, tat; D016328:NF-kappa B; D009569:Nitric Oxide; D004247:DNA; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse