Activation of NF-κB and p38 MAP Kinase Is Not Sufficient for Triggering Efficient HIV Gene Expression in Response to Stress

Abstract

Recent studies have established an essential role for p38 MAP kinase in UV activation of human immunodeficiency virus (HIV) gene expression. However, p38 MAP kinase is not involved in activation of NF-kappa B, a key transcriptional activator of HIV gene expression, in response to UV, suggesting that NF-kappa B acts independently of p38 MAP kinase. In this study, we have investigated whether activation of HIV gene expression occurs when p38 MAP kinase and NF-kappa B are activated by separate stress-causing treatments, each relatively specific for activating only one of the factors. Treatment of cells with sorbitol (hyperosmotic shock) strongly activates p38 MAP kinase, whereas the cytokine TNF-alpha is a poor activator of p38 MAP kinase. On the other hand, TNF-alpha is a strong activator of NF-kappa B whereas sorbitol is not. Sorbitol, however, activates AP-1 DNA binding activity in a manner similar to that of UV. Most importantly, both sorbitol and TNF-alpha are poor activators of HIV gene expression in HeLa cells stably transfected with an HIVcat reporter gene, whereas UV elicits a strong response. The combined treatment with UV and hyperosmotic shock produces an additive effect on HIV gene expression, suggesting that these agents activate at least in part by different mechanisms. The combined treatment with sorbitol and TNF-alpha activates p38 and NF-kappa B to levels similar to those with UV, yet only results in 25-30% of the CAT levels elicited by UV. Inhibition of NF-kappa B activation by the protease inhibitor N-alpha-tosyl-L-phenylalanine chloromethyl ketone (TPCK) prevents UV activation of HIV gene expression, but does not inhibit p38 MAP kinase activation. We conclude that whereas both p38 MAP kinase and NF-kappa B are important for UV activation of HIV gene expression they act independently from each other and activation of both factors is not sufficient for triggering a full HIV gene expression response. Activation of HIV gene expression by UV must therefore involve additional cellular processes, such as those triggered by DNA damage, for generation of a full gene expression response.

Activation of the Nuclear Factor κB Pathway by Astrocyte Elevated Gene-1: Implications for Tumor Progression and Metastasis

“…Several recent studies indicate that NF-nB is activated by various carcinogens and tumor promoters. These include benzo[a]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, UV radiation, ionizing radiation, and phorbol esters (7)(8)(9)(10)(11)(12)(13). For instance, UV radiation has been shown to cause sunburn reactions (swelling, leukocyte infiltration, epidermal hyperplasia, and accumulation of proinflammatory cytokines) leading to skin cancer, and suppression of NF-nB blocks the sunburn-induced damage (14).…”

Mood‐Enhancing Antidepressant St. John's Wort Inhibits the Activation of Human Immunodeficiency Virus Gene Expression by Ultraviolet Light

“…Agents such as sorbitol, TNF-α, and PMA, which are the potent activators of p38 MAP kinase or NF-κB alone, are not potent inducers of HIV-LTR in HeLa cells. Both p38 MAP kinase and NF-κB activation is required for a full HIV response by UV (14,17). How the p38 MAP kinase enzyme plays such an important role in activating HIV gene expression is not yet clear, but the two NF-κB-binding sites in the modulatory region of the HIV-LTR are critical for the activity of the HIV-1 promoter (21,25).…”

“…Blots were developed using the alkaline phosphatase/CDP-Star system, Perkin Elmer Life Sciences Inc. (Boston, MA), followed by exposure to x-ray film. The same blot was used to probe for equal loading of protein using antibodies to p38 MAP kinase or JNK or p44/42 MAP kinase as described (14,17 ). CAT assays were carried out as described (14)(15)(16)(17).…”

“…Nuclear extracts from HIVcat/HeLa cells were prepared from confluent 100-mm dishes as described (14)(15)(16)(17)(18). Briefly, cells from a 100-mm dish were washed and scraped in PBS and collected by slow-speed centrifugation.…”

“…Recently, we have shown that activation of p38 MAP kinase and NF-κB is necessary but not sufficient for triggering efficient HIV gene expression in response to UV (14,17). To investigate whether SJW is mediating its inhibitory effect on HIV gene expression by blocking the UV-induced p38 MAP kinase, we then examined p38 MAP kinase activation by Western blotting using phospho-specific p38 MAP kinase antibody.…”