Kaposi's sarcoma (KS)-associated herpesvirus (KSHV), also known as human herpesvirus 8, is an etiologic agent of KS, primary effusion lymphoma (PEL), and multicentric Castleman's disease. We recently demonstrated that hypoxia can induce lytic replication of KSHV in PEL cell lines. Hypoxia induces the accumulation of hypoxia-inducible factors (HIF), and we hypothesized that the KSHV genome may respond to hypoxia through functional hypoxia response elements (HREs). Here, we demonstrate the presence of at least two promoters within the KSHV genome that are activated by hypoxia or hypoxia mimics. One is in the promoter region of the gene for Rta, the main lytic switch gene, and the other is within the promoter region of ORF34, a lytic gene of unknown function. The ORF34 promoter contains three putative consensus HREs oriented in the direction of the gene. Dissection and site-directed mutagenesis studies confirmed that one of the HREs of the ORF34 promoter is functional. Under conditions of hypoxia, the ORF34 promoter was strongly upregulated by HIF-1␣ and HIF-2␣. By contrast, the promoter of the gene for Rta appeared to be preferentially upregulated by HIF-2␣. Reverse transcription-PCR analysis revealed that specific messages for ORF34 and ORF50 are upregulated in BCBL-1 cells exposed to hypoxia. An HIF-1 binding and competition assay demonstrated that the HRE sequence from the ORF34 promoter can compete for HIF-1␣ binding to an erythropoietin HRE oligonucleotide while a mutant sequence cannot. Thus, we demonstrated that a viral gene can be activated by hypoxia through activation of a functional viral HRE. To our knowledge, this is the first example of a functional HRE in a viral promoter.

Human herpesvirus 8 can be present in oral epithelial cells and is shed independent of the patient's immune status, indicating that oral HHV-8 shedding may occur at any time in HHV-8-seropositive individuals.

Expression of human herpesvirus 8 viral Bcl-2 protein was demonstrated in spindle cells of late-stage Kaposi's sarcoma lesions but not in primary effusion lymphoma cell lines. In contrast, strong expression of human Bcl-2 was found in stimulated primary effusion lymphoma cells, whereas in Kaposi's sarcoma lesions preferential mononuclear cells, and to a lesser extent spindle cells, stained positive.

Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday Large molecules adsorbed on surfaces can be analyzed by scanning tunneling microscopy (STM) under various environmental conditions: on a dry surface in air or vacuum, and at the solid-liquid interface. However, can measurements under dissimilar conditions be compared, e. g., when sample A was studied at the solid-liquid interface and sample B in a dry environment? Only rarely can the same substance be examined with more than one approach, since completely different set-up and preparations are necessary. Furthermore, few substances are suitable for several methods of sample preparation and characterization. We have chosen a large, flexible, nonplanar molecule, namely an alkoxy-substituted second-generation dendritic compound with a chiral core unit, which is peculiar for its −hourglass× conformation. The assembly properties have been explored by STM both in solution-cast self-organized monolayers (SOMs) and multilayer films, as well as at the solid-liquid interface. The complexity and limits of the three approaches applied to our hourglass-shaped dendritic compound are discussed. Depending on the approach and environmental conditions, several quality levels of image resolution could be achieved; measurements carried out at low temperatures led to highest resolution on the aromatic parts of the molecule. A comparison of equally sized images obtained under these varying conditions reveals not only different packing arrangements, but also spots of unlike shape. Therefore, when the approach, preparation, and/or environmental conditions are not the same, STM measurements of different compounds have to be compared with greatest care.