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Most raptor species rely on perches for hunting, resting, preening, and roosting, and in many agricultural areas the availability of adequate perches can limit raptor abundance and diversity. This has negative implications for both raptor conservation and for the provisioning of natural pest control services for farmers. Installing artificial perches on agricultural lands can therefore benefit both raptors and farmers, but perches must be installed in optimal locations to maximize raptor use and minimize unnecessary costs to farmers. We monitored raptor use of artificial perches in a California vineyard over winter using remote photography to compare two sets of perch types: perches at the top versus perches at the bottom of a steep hill, and perches located among trees versus perches located in an open area. We found that raptors preferred perches on hilltops over perches at the base of hills, and that raptors seem to prefer perches in open habitat over perches located adjacent to trees, although a small sample size for this comparison limited our analysis. more...

Stenotrophomonas maltophilia is an emerging, multidrug-resistant pathogen of increasing importance for the immunocompromised, including cystic fibrosis patients. Despite its significance as an emerging pathogen, relatively little is known regarding the specific factors and mechanisms that contribute to its pathogenicity. We identify and characterize a putative ankyrin-repeat protein (Smlt3054) unique to clinical S. maltophilia isolates that binds F-actin in vitro and co-localizes with actin in transfected HEK293a cells. Smlt3054 is endogenously expressed and secreted from clinical S. maltophilia isolates, but not an environmental isolate (R551-3). The in vitro binding of Smlt3054 to F-actin resulted in a thickening of the filaments as observed by TEM. Ectopic expression of Smlt3054-GFP exhibits strong co-localization with F-actin, with distinct, retrograde F-actin waves specifically associated with Smlt3054 in individual cells as well as formation of dense, internal inclusions at the expense of retrograde F-actin waves. Collectively, our results point to an interaction between Smlt3054 and F-actin. Furthermore, as a potentially secreted protein unique to clinical S. maltophilia isolates, Smlt3054 may serve as a starting point for understanding the mechanisms by which S. maltophilia has become an emergent pathogen. more...

Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8), has been linked to several malignancies in humans. KSHV is the etiologic agent associated with the development of Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD). KSHV is a double-stranded DNA virus that has been classified as a gammaherpesvirus. Here, we review the association of KSHV with human cancer, viral genes that may potentially be involved in the neoplastic process, and current therapies used to treat KS, PEL, and MCD. more...

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. Kaposi's sarcoma is the most common neoplasm among human immunodeficiency virus-positive individuals. Like other herpesviruses, KSHV is able to establish a predominantly latent, life-long infection in its host. The KSHV lytic cycle can be triggered by a number of stimuli that induce the expression of the key lytic switch protein, the replication and transcription activator (RTA) encoded by Orf50. The expression of Rta is necessary and sufficient to trigger the full lytic program resulting in the ordered expression of viral proteins, release of viral progeny, and host cell death. We have characterized an unknown open reading frame, Orf49, which lies adjacent and in the opposite orientation to Orf50. Orf49 is expressed during the KSHV lytic cycle and shows early transcription kinetics. We have mapped the 5′ and 3′ ends of the unspliced Orf49 transcript, which encodes a 30-kDa protein that is localized to both the nucleus and the cytoplasm. Interestingly, we found that Orf49 was able to cooperate with Rta to activate several KSHV lytic promoters containing AP-1 sites. The Orf49-encoded protein was also able to induce transcriptional activation through c-Jun but not the ATF1, ATF2, or CREB transcription factor. We found that Orf49 could induce phosphorylation and activation of the transcription factor c-Jun, the Jun N-terminal kinase (JNK), and p38. Our data suggest that Orf49 functions to activate the JNK and p38 pathways during the KSHV lytic cycle. more...

The K15 gene product of Kaposi's sarcoma-associated herpesvirus (KSHV) is a transmembrane protein that is encoded by the last open reading frame of the KSHV genome. The K15 protein has been implicated in modulation of B-cell signal transduction and activation of the Ras/mitogen-activated protein kinase and NF-κB signal transduction pathways. Here we report the identification of the transcriptional start site of the full-length K15 gene in KSHV-positive BCBL-1 cells. We have mapped the K15 transcriptional start site to a position 152 nucleotides upstream from the translation start site by rapid amplification of cDNA ends and RNase protection assays. We have also characterized the K15 promoter element. To analyze the cis -acting elements necessary to regulate K15 gene expression, a series of 5′ promoter deletion constructs were generated and subcloned upstream of the luciferase reporter gene. Transcriptional assays with these mutant promoters demonstrated that chemical induction in latently infected KSHV-positive BCBL-1 cells activated K15 transcription. In addition, K15 promoter transactivation was also mediated by the viral immediate-early protein Orf50/Rta, suggesting that the K15 gene is actively transcribed during lytic replication. more...

The transcription factor E2F and its regulation by pRB and related pocket proteins are central to cell cycle control in higher eukaryotes. Much of our knowledge of this regulation has come from studies using immediate-early proteins of DNA tumor viruses. Previously, we reported that the 72-kDa immediate-early region 1 gene product of the human cytomegalovirus, IE72, transactivates the dihydrofolate reductase promoter through the E2F site and that it physically interacts with E2F1 (M. J. Margolis, S. Pajovic, E. L. Wong, M. Wade, R. Jupp, J. A. Nelson, and J. C. Azizkhan, J. Virol. 69:7759-7767, 1995). In this study, we further characterized the mechanism by which IE72 modulates E2F-dependent transcription. In vitro phosphorylation reactions using gel-purified bacterially expressed proteins revealed that IE72 is a kinase that autophosphorylates and phosphorylates E2F1, -2, and -3 (but not E2F4 or -5) and the RB-related pocket proteins p130 and p107 (but not pRB). The region of IE72 spanning amino acids 173 to 197 shows a high level of homology to the ATP binding sites in over 500 kinases. The kinase-negative protein IE72deltaATP, from which this region has been deleted, cannot activate E2F-dependent transcription. The kinase activity of IE72 is also required for its ability to reduce the association of E2F4 with p107 and p130. Taken together, these data suggest that the kinase activity of IE72 is required for E2F-dependent transcriptional activation and that this is likely to result from phosphorylation of specific members of the E2F and pocket protein families by IE72. more...

CD4-IgG2 is a novel fusion protein comprising human IgG2 in which the Fv portions of both heavy and light chains have been replaced by the V1 and V2 domains of human CD4. This tetrameric protein is being developed as an immunoprophylactic agent to reduce the probability of infection following HIV-1 exposure, in settings such as occupational or perinatal exposure to the virus. CD4-IgG2 has been expressed in Chinese hamster ovary cells and is secreted as a fully assembled heterotetramer. The protein binds with nanomolar affinity to purified gp120 from both a laboratory-adapted strain and a primary isolate of HIV-1. Pharmacokinetic studies in rabbits demonstrated that CD4-IgG2 has a plasma terminal half-life greater than 1 day, compared with 15 min for soluble CD4 (sCD4). CD4-IgG2 does not bind to Fc receptors on the surface of U937 monocyte/macrophage cells. Compared to molecules that incorporate the Fc portion of IgG1, CD4-IgG2 has less potential to mediate functions such as antibody-dependent enhancement of infection or transplacental transmission of HIV-1. When tested in a virus-free HIV-1 envelope glycoprotein-mediated cell fusion assay, the tetrameric CD4-IgG2 molecule inhibited syncytium formation more effectively than monomeric sCD4 or a dimeric CD4-gamma 2 fusion protein. This suggests the protein will block cell-to-cell transmission of HIV-1. Moreover, CD4-IgG2 effectively neutralized a panel of laboratory-adapted strains and primary isolates of HIV-1, including strains with different tropisms and isolated from different stages of the disease, at concentrations that should be readily achieved in vivo. more...