Activation of human immunodeficiency virus gene expression by ultraviolet light in stably transfected human cells does not require the enhancer element

A quantitative bioassay for HIV-1 gene expression based on UV activation: effect of glycyrrhizic acid

Previous reports have shown that HIV-LTRcat constructs stably transfected in HeLa cells are inducible after exposure to UV light. We have optimized this system for studying the effect of drugs on HIV-1 gene expression. The maximum UV response was observed in quiescent stationary cells stimulated with fresh medium for 3h. Glycyrrhizic acid suppressed UV-induced HIV gene expression in a concentration-dependent manner. The inhibitory effect was strongest when GL was added immediately after UV exposure; it was still evident when GL was added at 5 h, it was completely lost at 10 h, after UV exposure. The inhibitory effect was even more pronounced if the cells were pretreated with sub-effective dose (0.0012 mM) of GL prior to UV exposure. The IC50 values with and without pretreatment were 0.04 and 0.38 mM, respectively. Cell proliferation and viability were not affected by GL at doses as high as 2.4 mM. The inhibitory effect of GL on UV-induced CAT activity correlated with the complete inhibition of binding activities of NF-kappaB p65, NF-kappaB p50, c-Fos, and c-Rel. Thus, the UV-based bioassay as proposed here can be exploited for the routine screening of the compounds that interfere with HIV-1 gene expression.

Induction of the gene encoding macrophage chemoattractant protein 1 by Orientia tsutsugamushi in human endothelial cells involves activation of transcription factor activator protein 1

Human macrophage chemoattractant protein 1 (MCP-1) is a potent mediator of macrophage migration and therefore plays an essential role in early events of inflammation. In endothelial cells, at least three independent pathways regulate MCP-1 expression by NF-kappaB and AP-1. Orientia tsutsugamushi causes vasculitis in humans by replicating inside macrophages and endothelial cells. In the present study, we investigated the cis-acting and trans-acting elements involved in O. tsutsugamushi-induced MCP-1 gene expression in human umbilical vein endothelial cells (HUVEC). Although NF-kappaB activation was observed in HUVEC infected with O. tsutsugamushi, inhibition of NF-kappaB activation did not affect the MCP-1 expression. However, treatment of HUVEC with extracellular signal-regulated kinase (ERK) kinase inhibitor or p38 mitogen-activated protein kinase (MAPK) inhibitor suppressed expression of MCP-1 mRNA concomitant with downregulation of activator protein 1 (AP-1) activation. Deletion of triphorbol acetate response elements (TRE) at position -69 to -63 of MCP-1 gene abolished inducible promoter activity. Deletion of TRE at position -69 to -63-96 to -90 or deletion of NF-kappaB-binding site at position -69 to -63-88 to -79 did not affect the inducibility of promoter. Site-directed mutagenesis of the NF-kappaB binding sites at positions -2640 to -2632, -2612 to -2603 in the enhancer region, or the AP-1 biding site at position -2276 to -2270 decreased the inducible activity of the promoter. Taken together, AP-1 activation by both the ERK pathway and the p38 MAPK pathway as well as their binding to TRE at position -69 to -63 in proximal promoter and TRE at position -2276 to -2270 in enhancer region is altogether essential in induction of MCP-1 mRNA in HUVEC infected with O. tsutsugamushi. Although NF-kappaB activation is not essential per se, the kappaB site in the enhancer region is important in MCP-1 induction of HUVEC. This discrepancy in the involvement of the NF-kappaB may be due to the function of chromatin structures and other transcription cofactors in the regulation of MCP-1 gene expression in response to O. tsutsugamushi infectioin.

Activation of HIV in human skin by ultraviolet B radiation and its inhibition by NFkappaB blocking agents

To determine whether ultraviolet B (UVB) irradiation leads to activation of HIV in human skin, we conducted prospective and controlled studies in two academic medical centers in Texas from July 1995 to April 1999. HIV-positive patients with UV-treatable skin diseases were enrolled at each center, 18 subjects at one and 16 at the other. In one center, specimens from lesional and nonlesional skin biopsies were taken before and after sham- or UVB-irradiation administered in vivo or in vitro. In the other center, UVB phototherapy was administered three times weekly and specimens from skin biopsies were taken before and after 2 weeks (six treatments). Cutaneous HIV load was assessed using reverse transcriptase-polymerase chain reaction and reverse transcriptase-polymerase chain reaction in situ hybridization. UVB irradiation led to a 6-10-fold increase in the number of HIV in skin. To ascertain a role for nuclear factor kappa B (NFkappaB) in UVB-inducible HIV activation, two types of blockers, NFkappaB oligonucleotide decoy and sodium salicylate, were tested; each inhibited UVB-inducible HIV activation in skin partially. We conclude that UVB irradiation leads to increased numbers of HIV in human skin via processes that include release of cytoplasmic NFkappaB.

Transcriptional activation of endogenous retroviral sequences in human epidermal keratinocytes by UVB irradiation

Ultraviolet radiation is a pathogenic factor in various diseases, e. g., autoimmune disorders such as lupus erythematosus. On the other hand, endogenous retroviruses are discussed as etiologic agents in lupus erythematosus. Therefore, we investigated the influence of ultraviolet irradiation on expression of human endogenous retroviral sequences and human endogenous retroviral sequence promoter-driven transcription of cellular genes using human epidermal keratinocytes as a model system. First, conserved sequences of endogenous retroviral pol genes were amplified from cellular mRNA by reverse transcriptase polymerase chain reaction with degenerate oligonucleotide primers. Polymerase chain reaction products were hybridized in a reverse dot blot hybridization assay to a representative number of distinct cloned human endogenous retroviral pol fragments. Using this method, we could show that irradiation with 30 mJ per cm2 ultraviolet B activates transcription of various endogenous retroviral pol sequences in primary epidermal keratinocytes as well as in a spontaneously immortalized keratinocyte cell line (HaCaT). Interestingly, some of these sequences were found to be closely related to pol sequences of human endogenous retroviral sequences which have been shown to be expressed in autoimmune patients. Analysis of human endogenous retroviral pol expression in vivo using skin biopsies of lupus erythematosus patients revealed similar activation patterns. In a second approach, ultraviolet B- induced chimeric transcripts were isolated which are initiated by human endogenous retroviral promoters and proceed into cellular sequences using a newly established modified differential display polymerase chain reaction technique. The activation of human endogenous retroviral sequence transcription by ultraviolet B may contribute to the pathogenesis of lupus erythematosus, where inappropriate antigenic presentation of ultraviolet B-induced viral and cellular proteins could stimulate autoantibody production.

Pathogenesis of non-AIDS-defining cancers: a review

As the AIDS epidemic advances, the number of HIV-infected subjects developing AIDS-related neoplasms is rapidly increasing, and the spectrum of malignancies encountered is expanding. Several non-AIDS-defining cancers are being reported at an increasing incidence in HIV-infected individuals, including anal, skin, oral mucosa, head and neck and lung carcinomas, testicular tumors, and pediatric soft-tissue sarcoma. There appears to be an emerging role for various concurrent viral infections in the HIV-infected host that are likely implicated in the pathogenesis of some nondefining-AIDS neoplasms. Our recent findings in HIV-associated lung cancers and in the precursor lesions of cervical carcinoma suggest that wide-spread genomic instability, as manifested by the development of increased numbers of microsatellite alterations (MAs), may occur frequently in HIV-associated tumors and they may play an important role in the pathogenesis of those neoplasms. Although the mechanism underlying the development of increased MAs is unknown, it may play a crucial role in the development of many HIV-associated tumors. It will be important to track the epidemiological and biological features of non-AIDS-defining cancers in HIV-infected patients, and compare them to those tumors in the general population. It is likely that further clues about malignant transformation and oncogenesis unraveled in the HIV setting will have broad clinical implications.

Nf-kappa B: an important transcription factor in photobiology

Increased gene expression as a consequence of environmental stress is typically observed in mammalian cells. In the past few years the cis- and trans-acting genetic elements responsible for gene induction by radiation (from UV-C to visible light) started to be well characterized. The molecular mechanisms involved in the cell response to radiation reveal that an important control occurs at the transcriptional level and is coordinated by various transcription factors. Among these transcription factors, the well-known Rel/NF-kappa B family of vertebrate transcription factors plays a pivotal role as it controls both the inflammatory and immune responses. The NF-kappa B family comprises a number of structurally related, interacting proteins that bind DNA as dimers and whose activity is regulated by subcellular location. This family includes many members (p50, p52, RelA, RelB, c-Rel, ...), most of which can form DNA-binding homo- or heterodimers. Nuclear expression and consequent biological action of the eukaryotic NF-kappa B transcription factor complex are tightly regulated through its cytoplasmic retention by ankyrin-rich inhibitory proteins known as I kappa B. In the best-characterized example, I kappa B-alpha interacts with a p50/RelA (NF-kappa B) heterodimer to retain the complex in the cytoplasm and inhibit its DNA-binding activity. Upon receiving a variety of signals, many of which are probably mediated by the generation of reactive oxygen species (ROS), I kappa B-alpha undergoes phosphorylation, is then ubiquitinated at nearby lysine residues and finally degraded by the proteasome, while still complexed with NF- kappa B. Removal of I kappa B-alpha uncovers the nuclear localization signals on subunits of NF-kappa B, allowing the complex to enter the nucleus, bind to DNA and affect gene expression. In this paper, we shall show that molecular mechanisms leading to NF-kappa B activation by UV or by photosensitization are initiated by oxidative damage at the membrane level or by the induction of DNA alterations. While the exact nature of the transduction intermediates is still unknown, we shall show that NF-kappa B activation by radiation follows different pathways from those used by pro-inflammatory cytokines.

TRIP: a novel double stranded RNA binding protein which interacts with the leucine rich repeat of flightless I

A northwestern screen of a CHO-K1 cell line cDNA library with radiolabelled HIV-1 TAR RNA identified a novel TAR RNA interacting protein, TRIP. The human trip cDNA was also cloned and its expression is induced by phorbol esters. The N-terminus of TRIP shows high homology to the coiled coil domain of FLAP, a protein which binds the leucine-rich repeat (LRR) of Flightless I (FLI) and the interaction of TRIP with the FLI LRR has been confirmed in vitro . TRIP does not bind single stranded DNA or RNA significantly and binds double stranded DNA weakly. In contrast, TRIP binds double stranded RNA with high affinity and two molecules of TRIP bind the TAR stem. The RNA binding domain has been identified and encompasses a lysine-rich motif. A TRIP-GFP fusion is localised in the cytoplasm and excluded from the nucleus. FLI has a C-terminal gelsolin-like domain which binds actin and therefore the association of TRIP with the FLI LRR may provide a link between the actin cytoskeleton and RNA in mammalian cells.

Nuclear and non-nuclear targets of genotoxic agents in the induction of gene expression. Shared principles in yeast, rodents, man and plants

The interplay between environmental cues and the genetic response is decisive for the development, health and well-being of an organism. For some environmental factors a narrow margin separates beneficial and toxic impacts. With the increasing exposure to UV-B this dichotomy has reached public attention. This review will be concerned with the mechanisms that mediate a cellular genetic response to noxious agents. The toxic stimuli find access to the regulatory network inside cells by interacting at several points with cellular molecules - a process that converts the 'outside information' into 'cellular language'. As a consequence of such interactions, many adverse agents cause massive signal transduction and changes of gene expression. There is an interesting conservation of the mechanisms from yeast to man. An understanding of the genetic programs and of their phenotypic consequences is lagging behind.

UVB phototherapy is an effective treatment for pruritus in patients infected with HIV

BACKGROUND

Pruritus in patients positive for HIV may be debilitating.

OBJECTIVE

Our purpose was to evaluate the efficacy of UVB therapy in the treatment of pruritus in patients positive for HIV.

METHODS

Twenty-one male HIV-positive patients with intractable pruritus (14 with eosinophilic folliculitis and 7 with primary pruritus) were treated three times weekly with UVB phototherapy. Pruritus was quantified with use of a subjective score of 0 (none) to 10 (severe).

RESULTS

Mean CD4 counts at the initiation of therapy were 91.0 +/- 31.9 cells/microliter. Pruritus scores before and after treatment were 8.6 +/- 0.4 and 2.2 +/- 0.5, respectively (p < 0.001). The mean number of treatments to achieve maximal improvement was 20.7 +/- 2.3, with a cumulative UVB dose of 3399.1 +/- 597.4 mJ/cm2. No significant difference was found between the group with eosinophilic folliculitis and the group with primary pruritus.

CONCLUSION

UVB phototherapy can produce significant relief of pruritus and improvement in the quality of life in patients positive for HIV.

Activation of the HIV-1 long terminal repeat by cytokines and environmental stress requires an active CSBP/p38 MAP kinase

The human immunodeficiency virus, type 1 (HIV-1) promoter is known to be activated by proinflammatory cytokines and UV light. These stimuli also activate various members of the mitogen-activated protein kinase family, including JNK/SAPK and CSBP/p38. In HeLa cells containing an integrated HIV-1 long terminal repeat (LTR) -driven reporter, we now show that the specific p38 inhibitor, SB203580, inhibits activation of the HIV-1 LTR by interleukin-1, tumor necrosis factor, UV light, and osmotic stress. Inhibition was 70-90% in all but the case of tumor necrosis factor stimulation, where inhibition was 50%. Each of these stimuli activated p38, which was inhibited by SB203580 in vitro and in vivo with an IC50 (between 0.1 and 1 microM) similar to that required to inhibit transcription. In contrast, SB203580 had no effect on JNK, which was also activated by these stimuli. The NFkappaB sites in the HIV-1 LTR were required for a response to cytokines but not to UV, and SB203580 remained capable of inhibiting UV activation in the absence of the NFkappaB sites. Studies in which SB203580 was added at different times relative to UV stimulation suggested that the critical p38-mediated phosphorylation event occurred between 2 and 4 h after UV treatment. These data indicate that p38 is required for HIV-1 LTR activation but that the action of p38 is delayed, presumably due to substrate unavailability or inaccessibility.

Signal transduction and HIV transcriptional activation after exposure to ultraviolet light and other DNA-damaging agents

Short wavelength (254 nm) ultraviolet light (UVC) radiation was much more potent in activating transcription of human immunodeficiency virus 1 (HIV) reporter genes stably integrated into the genomes of human and monkey cells than ionizing radiation (IR) from a 137Cs source at similarly cytotoxic doses. A similar differential was also observed when c-jun transcription levels were examined. However, these transcription levels do not correlate with activation of nuclear factor (NF)-kappa B and AP-1 measured by band-shift assays, i.e. both types of radiation produce similar increases in NF-kappa B and AP-1 activity, suggesting existence of additional levels of regulation during these responses. Because of the well-established involvement of cytoplasmic signaling pathways in the cellular response to tumor necrosis factor-alpha (TNF-alpha), UVC, and IR using other types of assays, the role of TNF-alpha in the UVC response of HIV and c-jun was investigated in our cell system. We demonstrate that UVC and TNF-alpha activate HIV gene expression in a synergistic fashion, suggesting that it is unlikely that TNF-alpha is involved in UVC activation of HIV transcription in stably transfected HeLa cells. Moreover, maximum TNF-alpha stimulation resulted in one order of magnitude lower levels of HIV expression than that observed after UVC exposure. We also observed an additive effect of UVC and TNF-alpha on c-jun steady-state mRNA levels, suggestive of a partial overlap in activation mechanism of c-jun by UVC and TNF-alpha; yet these responses are distinct to some extent. Our results indicate that the HIV, and to some extent also the c-jun, transcriptional responses to UVC are not the result of TNF-alpha stimulation and subsequent downstream cytoplasmic signaling events in HeLa cells. Additional levels of regulation that do not directly involve the NF-kappa B and AP-1 transcription factors, such as changes in chromatin structure associated with the UV repair process, may also be important for a full transcriptional response of HIV and c-jun to UVC. In addition to the new data, this report also summarizes our current views regarding UVC-induced activations of HIV gene expression in stably transfected cells.

Psoralen photobiology: recent advances

Clinical efficacy may arise from psoralen-induced photodamage by the induction of a panoply of biomolecules. In cellular studies with UV or photoactivatable agents, the activation of NF-kappa B, probably the most widely studied transcription factor, occurs after its release from an inhibiting factor, I kappa B. The activation of transcription factors has also been correlated with the UV absorption spectrum of DNA (35). Furthermore, it was shown that the photoadducts do not need to be processed or repaired because transcription factor induction is observed in repair-deficient cells. In these latter cells lower UV doses are required to induce these transcription factors. As a result of transcription factor induction, treated cells may have a greater number of class I molecules on their surface and an altered cytokine profile. It is possible (and likely) that these effects occur in different cells to different extents. The important message is that activational events may occur that could alter the cell's (or cells') ability to regulate a disease process. Many studies have shown that the time frame for this type of damage-induced event may range from seconds to minutes (36). Clearly 8-MOP/UVA-induced events such as those described above could be initiated as the result of a single photochemotherapy session.