Affinity-based screening of MDM2/MDMX-p53 interaction inhibitors by chemical array: Identification of novel peptidic inhibitors.

MDM2 and MDMX are oncoproteins that negatively regulate the activity and stability of the tumor suppressor protein p53. The inhibitors of protein-protein interactions (PPIs) of MDM2-p53 and MDMX-p53 represent potential anticancer agents. In this study, a novel approach for identifying MDM2-p53 and MDMX-p53 PPI inhibitor candidates by affinity-based screening using a chemical array has been established. A number of compounds from an in-house compound library, which were immobilized onto a chemical array, were screened for interaction with fluorescence-labeled MDM2 and MDMX proteins. The subsequent fluorescent polarization assay identified several compounds that inhibited MDM2-p53 and MDMX-p53 interactions

Rapid detection of hypoxia-inducible factor-1-active tumours: pretargeted imaging with a protein degrading in a mechanism similar to hypoxia-inducible factor-1alpha

PURPOSE: Hypoxia-inducible factor-1 (HIF-1) plays an important role in malignant tumour progression. For the imaging of HIF-1-active tumours, we previously developed a protein, POS, which is effectively delivered to and selectively stabilized in HIF-1-active cells, and a radioiodinated biotin derivative, (3-(123)I-iodobenzoyl)norbiotinamide ((123)I-IBB), which can bind to the streptavidin moiety of POS. In this study, we aimed to investigate the feasibility of the pretargeting method using POS and (123)I-IBB for rapid imaging of HIF-1-active tumours. METHODS: Tumour-implanted mice were pretargeted with POS. After 24 h, (125)I-IBB was administered and subsequently, the biodistribution of radioactivity was investigated at several time points. In vivo planar imaging, comparison between (125)I-IBB accumulation and HIF-1 transcriptional activity, and autoradiography were performed at 6 h after the administration of (125)I-IBB. The same sections that were used in autoradiographic analysis were subjected to HIF-1alpha immunohistochemistry. RESULTS: (125)I-IBB accumulation was observed in tumours of mice pretargeted with POS (1.6%ID/g at 6 h). This result is comparable to the data derived from (125)I-IBB-conjugated POS-treated mice (1.4%ID/g at 24 h). In vivo planar imaging provided clear tumour images. The tumoral accumulation of (125)I-IBB significantly correlated with HIF-1-dependent luciferase bioluminescence (R=0.84, p<0.01). The intratumoral distribution of (125)I-IBB was heterogeneous and was significantly correlated with HIF-1alpha-positive regions (R=0.58, p<0.0001). CONCLUSION: POS pretargeting with (123)I-IBB is a useful technique in the rapid imaging and detection of HIF-1-active regions in tumours

MDM2 is a novel E3 ligase for HIV-1 Vif

The human immunodeficiency virus type 1 (HIV-1) Vif plays a crucial role in the viral life cycle by antagonizing a host restriction factor APOBEC3G (A3G). Vif interacts with A3G and induces its polyubiquitination and subsequent degradation via the formation of active ubiquitin ligase (E3) complex with Cullin5-ElonginB/C. Although Vif itself is also ubiquitinated and degraded rapidly in infected cells, precise roles and mechanisms of Vif ubiquitination are largely unknown. Here we report that MDM2, known as an E3 ligase for p53, is a novel E3 ligase for Vif and induces polyubiquitination and degradation of Vif. We also show the mechanisms by which MDM2 only targets Vif, but not A3G that binds to Vif. MDM2 reduces cellular Vif levels and reversely increases A3G levels, because the interaction between MDM2 and Vif precludes A3G from binding to Vif. Furthermore, we demonstrate that MDM2 negatively regulates HIV-1 replication in non-permissive target cells through Vif degradation. These data suggest that MDM2 is a regulator of HIV-1 replication and might be a novel therapeutic target for anti-HIV-1 drug

Relationship between Symptoms and Gene Expression Induced by the Infection of Three Strains of Rice dwarf virus

BACKGROUND: Rice dwarf virus (RDV) is the causal agent of rice dwarf disease, which often results in severe yield losses of rice in East Asian countries. The disease symptoms are stunted growth, chlorotic specks on leaves, and delayed and incomplete panicle exsertion. Three RDV strains, O, D84, and S, were reported. RDV-S causes the most severe symptoms, whereas RDV-O causes the mildest. Twenty amino acid substitutions were found in 10 of 12 virus proteins among three RDV strains. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed the gene expression of rice in response to infection with the three RDV strains using a 60-mer oligonucleotide microarray to examine the relationship between symptom severity and gene responses. The number of differentially expressed genes (DEGs) upon the infection of RDV-O, -D84, and -S was 1985, 3782, and 6726, respectively, showing a correlation between the number of DEGs and symptom severity. Many DEGs were related to defense, stress response, and development and morphogenesis processes. For defense and stress response processes, gene silencing-related genes were activated by RDV infection and the degree of activation was similar among plants infected with the three RDV strains. Genes for hormone-regulated defense systems were also activated by RDV infection, and the degree of activation seemed to be correlated with the concentration of RDV in plants. Some development and morphogenesis processes were suppressed by RDV infection, but the degree of suppression was not correlated well with the RDV concentration. CONCLUSIONS/SIGNIFICANCE: Gene responses to RDV infection were regulated differently depending on the gene groups regulated and the strains infecting. It seems that symptom severity is associated with the degree of gene response in defense-related and development- and morphogenesis-related processes. The titer levels of RDV in plants and the amino acid substitutions in RDV proteins could be involved in regulating such gene responses

Diversity and Transformation of Aid Patterns in Asia\u27s "Emerging Donors"

This paper analyses comparatively the aid patterns and their formulation of four emerging donor countries: China, South Korea, Thailand and India. The aim of the paper is to increase understanding of how these countries’ aid patterns have been created and by what factors. The aid patterns employed by the emerging donors are divergent. Chinese aid has shifted from the overtly political and ideological to the commercialist; thus, current Chinese aid is closely tied to Chinese state owned enterprises (SOEs). Korean aid has consistently been commercialist, but recently it has incorporated universal and humanitarian considerations. Thailand has maintained a keen interest in aid as a stabiliser of its neighbouring countries. The Indian aid program was initially formed during the Cold War consonant with the ideology of the Non-Aligned Movement, but from the 1990s economic considerations became more important. Indian aid is influenced also by regional strategies, namely the stabilisation of neighbouring countries. Various factors are proposed to account for the formation and transformation of the aid patterns. Current Chinese aid is influenced by deepening economic interdependence and by diplomatic competition with Taiwan. Korean aid is promoted by pragmatic values and more recently by universal humanitarian values. The recent shift to a humanitarian emphasis is explained by a shift in the relative power balance of actors away from the conservative toward the progressive. In addition, its middle power status in the international community makes South Korea sensitive to competition from other donors, such as China, and to international pressure from DAC. Thai aid is motivated by the economic gap between Thailand and its neighbouring countries, by its strategies toward the Indo-China region, and by its compliance with DAC. The Indian aid program was initially formed during the Cold War in response to the political and ideological Non-Aligned Movement, but from the 1990s economic considerations became more important. India is also influenced by regional strategies, namely the stabilisation of neighbouring countries. This comparative analysis of these four emerging donors contributes to an understanding of the diversity of aid patterns and the particular factors that create them. The increasing diversity of aid patterns further implies potential for future pluralism of aid

An Institutional Analysis of Foreign Aid in Cambodia

Debate about the role and impact of the so-called “emerging donors” is becoming increasingly heated. The common reaction to these new donors, distinct from that accorded traditional donors, has had the unfortunate effect of obscuring two important aspects of the evolving aid landscape: 1) commonalities between the emerging donors and traditional Development Assistance Committee (DAC) donors; and 2) an evident diversity among the emerging donors. The biases at play are derived not only from a lack of sufficient information about how these new donors operate on the ground, but also from a lack of effort to integrate and analyze information that is available. This paper examines the impact of four emerging donors — China, India, the Republic of Korea (hereinafter referred to as “Korea”), and Thailand — on Cambodia‟s development, with a specific focus on the processes of aid provision by these new donors. By accounting for the experiences of the recipient country, this paper also challenges the conventional view that aid fragmentation should be reduced a priori