Induction of the interferon (IFN)-alpha/beta gene transcription in virus-infected cells is an event central to innate immunity. Mice lacking the transcription factor IRF-3 are more vulnerable to virus infection. In embryonic fibroblasts, virus-induced IFN-alpha/beta gene expression levels are reduced and the spectrum of the IFN-alpha mRNA subspecies altered. Furthermore, cells additionally defective in IRF-7 expression totally fail to induce these genes in response to infections by any of the virus types tested. In these cells, a normal profile of IFN-alpha/beta mRNA induction can be achieved by coexpressing both IRF-3 and IRF-7. These results demonstrate the essential and distinct roles of thetwo factors, which together ensure the transcriptional efficiency and diversity of IFN-alpha/beta genes for the antiviral response.

The interferon regulatory factor (IRF) family of transcription factors regulate the interferon (IFN) system, among which IRF-3 is involved in the virus-induced IFN-L L gene expression. Here we show that another member IRF-7 is critical for the IFN-K K gene induction. Unlike the IRF-3 gene, the IRF-7 gene is induced by IFNs through activation of the ISGF3 transcription factor, and IRF-7 undergoes virus-induced nuclear translocation. In cells lacking p48, an essential component of IFN stimulated gene factor 3 (ISGF3), ectopic expression of IRF-7 but not IRF-3 can rescue the deficiency to induce IFN-K K genes. These results indicate that IRF-7 is a key factor in the positive feedback regulation of IFN-K K/L L production.z 1998 Federation of European Biochemical Societies.

CpG island promoter methylation of tumor suppressor genes is one of the most characteristic abnormalities in EBVassociated gastric carcinoma (GC). Aberrant promoter methylation and expression loss of PTEN were evaluated in cancer tissues of GC by methylation-specific PCR and immunohistochemistry, respectively, showing that both abnormalities occurred concurrently in EBV-associated GC. PTEN abnormalities were reiterated in GC cell lines MKN-1 and MKN-7 infected with recombinant EBV, and DNA methyltransferase 1 (DNMT1) was commonly overexpressed in both cell lines. Stable and transient transfection systems in MKN-1 similarly showed that viral latent membrane protein 2A (LMP2A) upregulated DNMT1, leading to an increase in methylation of the PTEN promoter. Importantly, the level of phosphorylated signal transducer and activator of transcription 3 (pSTAT3) increased in the nuclei of LMP2A-expressing GC cells, and knockdown of STAT3 counteracted LMP2A-mediated DNMT1 overexpression. Immunohistochemistry for both pSTAT3 and DNMT1 showed diffuse labeling in the nuclei of the cancer cells in GC tissues, especially in EBV-associated GC. Taken together, LMP2A induces the phosphorylation of STAT3, which activates DNMT1 transcription and causes PTEN expression loss through CpG island methylation of the PTEN promoter in EBV-associated GC. LMP2A plays an essential role in the epigenetic abnormalities in host stomach cells and in the development and maintenance of EBV-associated cancer.

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digested by collagenase/trypsin, and the digested cardiac cells were allowed to attach to the plates overnight. The attached cells included macrophages and myofibroblasts (positive for α smooth muscle actin [αSMA]) as well as other cardiac cells (Supplemental Figure 1B). Notably, cardiac myofibroblasts seemed to be more difficult than cardiac macrophages to collect using our isolation method from infarcted hearts because, as revealed by our immunohistochemical analysis, the number of cardiac myofibroblasts was the same as that of cardiac macrophages in the infarcted area (Supplemental Figure 1C). When the overnight-attached cells were cultured in 10% FBS/DMEM for more than 6 days, almost all of the cells on the plates were positive for αSMA and SM22α, 2 myofibroblast marker proteins (18, 19) (>97.9% and >93.8%, respectively) (Supplemental Figure 1, D and E), indicating that the cells were primarily composed of cardiac myofibroblasts. This is probably because only myofibroblasts were able to grow rapidly in the culture medium.Isolated cardiac macrophages and myofibroblasts were allowed to engulf fluorescently labeled apoptotic cells, and we assessed the fluorescence taken up by cardiac macrophages and administration promoted the restoration of cardiac function and morphology after MI, suggesting that MFG-E8 is a new therapeutic target for the treatment of MI.