Regulation of the MYC oncogene remains unclear. Using 10058-F4, a compound that inhibits MYC-MAX transcription factor, MYC protein and gene expression were down-regulated in Namalwa cells, a Burkitt lymphoma. Compound 10058-F4 decreased MYC mRNA (45%), MYC protein (50%), and cell growth (32%). MYC-MAX transcription factor was disrupted 24 h after treatment, resulting in transcriptional inhibition of target genes. Because microRNAs (miRNA) disrupt mRNA translation, let-7a, let-7b, and mir-98 were selected using bioinformatics for targeting MYC. Inhibition of MYC-MAX transcription factor with 10058-F4 increased levels of members of the let-7 family. In inhibited cells at 24 h, let-7a, let-7b, and mir-98 were induced 4.9-, 1.3-, and 2.4-fold, respectively, whereas mir-17-5p decreased 0.23-fold. These results were duplicated using microRNA multianalyte suspension array technology. Regulation of MYC mRNA by let-7a was confirmed by transfections with pre-let-7a. Overexpression of let-7a (190%) decreased Myc mRNA (70%) and protein (75%). Down-regulation of Myc protein and mRNA using siRNA MYC also elevated let-7a miRNA and decreased Myc gene expression. Inverse coordinate regulation of let-7a and mir-17-5p versus Myc mRNA by 10058-F4, pre-let-7a, or siRNA MYC suggested that both miRNAs are Myc-regulated. This supports previous results in lung and colon cancer where decreased levels of the let-7 family resulted in increased tumorigenicity. Here, pre-let-7a transfections led to downregulation of expression of MYC and its target genes and antiproliferation in lymphoma cells. These findings with let-7a add to the complexity of MYC regulation and suggest that dysregulation of these miRNAs participates in the genesis and maintenance of the lymphoma phenotype in Burkitt lymphoma cells and other MYC-dysregulated cancers. [Cancer Res 2007;67(20):9762-70]

Human uterine leiomyomas (ULMs) are the most common neoplasms of women. Many genes are dysregulated in ULMs and some of this dysregulation may be due to abnormal expression of micro-RNAs (miRNAs). In this study, 55 ULMs and matched myometrium were collected from 41 patients for microarray-based global miRNA expression analysis. Of 206 miRNAs examined, 45 miRNAs were significantly up- or down-regulated in ULMs in comparison to the matched myometrium (P < 0.001). The top five dysregulated miRNAs in ULMs are the let-7 family, miR-21, miR-23b, miR-29b, and miR-197. Four polycistronic clusters of miRNAs were either up- or down-regulated, but not in a mixed pattern, indicative of coordinated regulation of these miRNAs. Significance analysis revealed that subsets of miRNAs were strongly associated with tumor sizes and race. By prediction analysis we identified some important tumorigenic genes previously identified in ULMs that may be targeted by the dysregulated miRNAs. HMGA2 was identified as one of target genes of the let-7 family of miRNAs and has been found to be suppressed by let-7 in vitro. This article contains Supplementary material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

Mycobacterium tuberculosis is the causative agent of tuberculosis, a disease that together with human immunodeficiency virus (HIV) and malaria, is one of the main causes of mortality due to an infectious agent (31). According to the WHO, onethird of the world's population is infected asymptomatically with M. tuberculosis, representing a large reservoir of infection (11). To block further transmission and reactivation in the already-infected population, it is necessary to develop improved intervention strategies that require a better understanding of the host-pathogen interaction.Infection of a mammalian host by M. tuberculosis usually occurs by the aerosol route, and the lung is typically the principal organ affected. The bacteria initially reside in alveolar macrophages (18), where they are usually able to replicate. In order to identify M. tuberculosis components that may be responsible for successful bacterial intracellular survival, many individual genes whose expression levels are up regulated by the microorganism inside the phagosome have been analyzed (16). DNA microarray technology has made it possible to analyze the M. tuberculosis global transcriptional response to different stimuli. Experiments have been carried out in broth culture, using conditions that may mimic the macrophage environment (i.e., low pH, cell wall stress, starvation, hypoxia, heat shock, etc.) in resting or activated mouse macrophages, and in vivo, using the mouse lung model of infection. The results of these studies have recently been reviewed (2, 29). The complete gene expression profile of M. tuberculosis growing in mouse macrophages was defined by Schnappinger et al. tuberculosis has to face a DNA-and cell envelope-damaging environment that is rich in fatty acid and deficient in iron. The transcriptional profile of M. tuberculosis infecting human lungs indicates that the bacteria regulate genes involved in the evasion of the immune system (45). A similar analysis of M. tuberculosis in human monocyte-derived macrophages after 7 days of infection suggested the relevance of bacterial genes involved in transcriptional regulation (8). In addition, M. tuberculosis genes that are essential for the survival of bacteria in mouse macrophages and in mouse lungs have been identified by using the transposon site hybridization technique (46) and designer arrays for defined mutant analysis (30).In this work, we analyzed the gene expression profile of M. tuberculosis strain H37Rv infecting human macrophage-like THP-1 cells. These cells treated with phorbol-myristate acetate (PMA) differentiate into mature macrophages, providing a good model for analyzing the interaction of M. tuberculosis with primary macrophages in terms of receptor expression, bacterial uptake, survival, and replication (59). It has been demonstrated that after infection with M. tuberculosis, THP-1 cells, in a manner similar to that of monocyte-derived macrophages, produce low levels of oxygen radicals and do not produce nitric oxide (55). Moreover, THP-1 cells are a good mod...

Mycobacterium tuberculosis survives in macrophages and usually subverts the bactericidal mechanisms of these phagocytes. The understanding of this host-pathogen interaction is relevant for the development of new treatments for tuberculosis. The adaptation of M. tuberculosis to intracellular life depends on its ability to regulate the expression of its genes. Sigma factors are important bacterial transcription activators that bind to the RNA polymerase and give it promoter specificity. Sigma factor E (SigE) controls the expression of genes that are essential for virulence. We have identified the SigE regulon during infection of macrophages, and we analyzed the impact of this regulon on the transcriptional response of phagocytes. Our results indicate that SigE regulates the expression of genes involved in the maintenance of M. tuberculosis cell envelope integrity and function during macrophage infection. Analysis of the phagocytes' transcriptional response indicates that the SigE regulon is involved in the modulation of the inflammatory response.

Lytic reactivation from latency is critical for the pathogenesis of Kaposi's sarcoma-associated herpesvirus (KSHV). We previously demonstrated that the 691-amino-acid (aa) KSHV Rta transcriptional transactivator is necessary and sufficient to reactivate the virus from latency. Viral lytic cycle genes, including those expressing additional transactivators and putative oncogenes, are induced in a cascade fashion following Rta expression. In this study, we sought to define Rta's direct targets during reactivation by generating a conditionally nuclear variant of Rta. Wild-type Rta protein is constitutively localized to cell nuclei and contains two putative nuclear localization signals (NLSs). Only one NLS (NLS2; aa 516 to 530) was required for the nuclear localization of Rta, and it relocalized enhanced green fluorescent protein exclusively to cell nuclei. The results of analyses of Rta NLS mutants demonstrated that proper nuclear localization of Rta was required for transactivation and the stimulation of viral reactivation. RTA with NLS1 and NLS2 deleted was fused to the hormone-binding domain of the murine estrogen receptor to generate an Rta variant whose nuclear localization and ability to transactivate and induce reactivation were tightly controlled posttranslationally by the synthetic hormone tamoxifen. We used this strategy in KSHV-infected cells treated with protein synthesis inhibitors to identify direct transcriptional targets of Rta. Rta activated only eight KSHV genes in the absence of de novo protein synthesis. These direct transcriptional targets of Rta were transactivated to different levels and included the genes nut-1/PAN, ORF57/Mta, ORF56/Primase, K2/viral interleukin-6 (vIL-6), ORF37/SOX, K14/vOX, K9/vIRF1, and ORF52. Our data suggest that the induction of most of the KSHV lytic cycle genes requires additional protein expression after the expression of Rta.Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus-8) is the etiologic agent of the human cancers primary effusion lymphoma (PEL) and Kaposi's sarcoma (KS) (8,22). Since B-cell infection predicts future KS development and latent KSHV infection is established before KS onset, the reactivation of productive (lytic) KSHV infection from the latently infected B-cell reservoir is a necessary step in KS development (2,51,54,78). Deciphering the mechanisms that function at the molecular level to control KSHV reactivation is therefore essential for understanding the pathogenesis of the virus.During KSHV reactivation in PEL tissue culture models, de novo expression of viral genes unfolds sequentially in a cascade fashion (31,44). A fraction of the cells in which the virus initiates reactivation support completion of the gene expression program, resulting in the production of progeny virus and lysis of the host cells (46,47,60). The reactivation program has thus been termed the KSHV lytic cycle. Similarly to other DNA viruses, the KSHV lytic cycle genes have been classified as immediate early (IE), delayed early (DE), or late (L...

Many neurodegenerative disorders are characterized by two pathological hallmarks: progressive loss of neurons and occurrence of inclusion bodies containing ubiquitinated proteins. Inflammation may be critical to neurodegeneration associated with ubiquitin-protein aggregates. We previously showed that prostaglandin J2 (PGJ2), one of the endogenous products of inflammation, induces neuronal death and the accumulation of ubiquitinated proteins into distinct aggregates. We now report that temporal microarray analysis of human neuroblastoma SK-N-SH revealed that PGJ2 triggered a "repair" response including increased expression of heat shock, protein folding, stress response, detoxification and cysteine metabolism genes. PGJ2 also decreased expression of cell growth/maintenance genes and increased expression of apoptotic genes. Over time prodeath responses prevailed over pro-survival responses, leading to cellular demise. Furthermore, PGJ2 increased the expression of proteasome and other ubiquitin-proteasome pathway genes. This increase failed to overcome PGJ2 inhibition of 26 S proteasome activity. Ubiquitinated proteins are degraded by the 26 S proteasome, shown here to be the most active proteasomal form in SK-N-SH cells. We demonstrate that PGJ2 impairs 26 S proteasome assembly, which is an ATP-dependent process. PGJ2 perturbs mitochondrial function, which could be critical to the observed 26 S proteasome disassembly, suggesting a cross-talk between mitochondrial and proteasomal impairment. In conclusion neurotoxic products of inflammation, such as PGJ2, may play a role in neurodegenerative disorders associated with the aggregation of ubiquitinated proteins by impairing 26 S proteasome activity and inducing a chain of events that culminates in neuronal cell death. Temporal characterization of these events is relevant to understanding the underlying mechanisms and to identifying potential early biomarkers.

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Introduction Epstein-Barr virus (EBV) is present in over 90% of the world's population. This infection is considered benign, even though in limited cases EBV is associated with infectious and neoplastic conditions. Over the past decade, the EBV association with breast cancer has been constantly debated. Adding to this clinical and biological uncertainty, different techniques gave contradictory results for the presence of EBV in breast carcinoma specimens. In this study, minor groove binding (MGB)-TaqMan real time PCR was used to detect the presence of EBV DNA in both peripheral blood and tumor samples of selected patients.