The nuclear GYF protein CD2BP2/U5-52K is required for T cell homeostasis.

The question whether interference with the ubiquitous splicing machinery can lead to cell-type specific perturbation of cellular function is addressed here by T cell specific ablation of the general U5 snRNP assembly factor CD2BP2/U5-52K. This protein defines the family of nuclear GYF domain containing proteins that are ubiquitously expressed in eukaryotes with essential functions ascribed to early embryogenesis and organ function. Abrogating CD2BP2/U5-52K in T cells, allows us to delineate the consequences of splicing machinery interferences for T cell development and function. Increased T cell lymphopenia and T cell death are observed upon depletion of CD2BP2/U5-52K. A substantial increase in exon skipping coincides with the observed defect in the proliferation/differentiation balance in the absence of CD2BP2/U5-52K. Prominently, skipping of exon 7 in Mdm4 is observed, coinciding with upregulation of pro-apoptotic gene expression profiles upon CD2BP2/U5-52K depletion. Furthermore, we observe enhanced sensitivity of naïve T cells compared to memory T cells to changes in CD2BP2/U5-52K levels, indicating that depletion of this general splicing factor leads to modulation of T cell homeostasis. Given the recent structural characterization of the U5 snRNP and the crosslinking mass spectrometry data given here, design of inhibitors of the U5 snRNP conceivably offers new ways to manipulate T cell function in settings of disease.

AML-specific cytotoxic antibodies in patients with durable graft-versus-leukemia responses.

Most patients with acute myeloid leukemia (AML) can only be cured when allogeneic hematopoietic stem-cell transplantation induces a graft-versus-leukemia immune response (GVL). Although the role of T cells and natural killer cells in tumor immunology has been established, less is known about the contribution of B cells. From B cells of high-risk patients with AML with potent and lasting GVL responses, we isolated monoclonal antibodies directed against antigens expressed on the cell surface of AML cells but not on normal hematopoietic and nonhematopoietic cells. A number of these donor-derived antibodies recognized the U5 snRNP200 complex, a component of the spliceosome that in normal cells is found in the cell. In AML however, the U5 snRNP200 complex is exposed on the cell membrane of leukemic blasts. U5 snRNP200 complex-specific antibodies induced death of AML cells in an Fc receptor-dependent way in the absence of cytotoxic leukocytes or complement. In an AML mouse model, treatment with U5 snRNP200 complex-specific antibodies led to significant tumor growth inhibition. Thus, donor-derived U5 snRNP200 complex-recognizing AML-specific antibodies may contribute to antitumor responses.

Functional analysis of a novel glioma antigen, EFTUD1.

BACKGROUND: A cDNA library made from 2 glioma cell lines, U87MG and T98G, was screened by serological identification of antigens by recombinant cDNA expression (SEREX) using serum from a glioblastoma patient. Elongation factor Tu GTP binding domain containing protein 1 (EFTUD1), which is required for ribosome biogenesis, was identified. A cancer microarray database showed overexpression of EFTUD1 in gliomas, suggesting that EFTUD1 is a candidate molecular target for gliomas. METHODS: EFTUD1 expression in glioma cell lines and glioma tissue was assessed by Western blot, quantitative PCR, and immunohistochemistry. The effect on ribosome biogenesis, cell growth, cell cycle, and induction of apoptosis and autophagy in glioma cells during the downregulation of EFTUD1 was investigated. To reveal the role of autophagy, the autophagy-blocker, chloroquine (CQ), was used in glioma cells downregulating EFTUD1. The effect of combining CQ with EFTUD1 inhibition in glioma cells was analyzed. RESULTS: EFTUD1 expression in glioma cell lines and tissue was higher than in normal brain tissue. Downregulating EFTUD1 induced G1 cell-cycle arrest and apoptosis, leading to reduced glioma cell proliferation. The mechanism underlying this antitumor effect was impaired ribosome biogenesis via EFTUD1 inhibition. Additionally, protective autophagy was induced by glioma cells as an adaptive response to EFTUD1 inhibition. The antitumor effect induced by the combined treatment was significantly higher than that of either EFTUD1 inhibition or CQ alone. CONCLUSION: These results suggest that EFTUD1 represents a novel therapeutic target and that the combination of EFTUD1 inhibition with autophagy blockade may be effective in the treatment of gliomas.

Comparative genomics RNAi screen identifies Eftud2 as a novel regulator of innate immunity.

The extent of the innate immune response is regulated by many positively and negatively acting signaling proteins. This allows for proper activation of innate immunity to fight infection while ensuring that the response is limited to prevent unwanted complications. Thus mutations in innate immune regulators can lead to immune dysfunction or to inflammatory diseases such as arthritis or atherosclerosis. To identify novel innate immune regulators that could affect infectious or inflammatory disease, we have taken a comparative genomics RNAi screening approach in which we inhibit orthologous genes in the nematode Caenorhabditis elegans and murine macrophages, expecting that genes with evolutionarily conserved function also will regulate innate immunity in humans. Here we report the results of an RNAi screen of approximately half of the C. elegans genome, which led to the identification of many candidate genes that regulate innate immunity in C. elegans and mouse macrophages. One of these novel conserved regulators of innate immunity is the mRNA splicing regulator Eftud2, which we show controls the alternate splicing of the MyD88 innate immunity signaling adaptor to modulate the extent of the innate immune response.

Anti-U5 snRNP antibody as a possible serological marker for scleroderma-polymyositis overlap.

OBJECTIVE: To determine the prevalence of the anti-U5 small nuclear ribonucleoprotein (snRNP) antibody in patients with systemic sclerosis. METHODS: Sera from 281 patients with systemic sclerosis, including 10 patients with overlapping polymyositis, were assayed using RNA immunoprecipitation and protein immunoprecipitation. RESULTS: Only one serum sample showed precipitation of U5 snRNA with scarce precipitation of U2, U1, U4 and U6 snRNAs. In addition, the serum precipitated a 200 kDa protein. The serum was from a 35-yr-old Japanese male patient with overlapping systemic sclerosis and polymyositis accompanied by large-cell lung carcinoma. The clinical appearance was similar to that of a case reported previously. CONCLUSION: The presence of the anti-U5 snRNP antibody in serum may be specific for scleroderma-polymyositis overlap syndrome.

Anti-U5 small nuclear ribonucleoprotein (snRNP) antibodies: a rare anti-U snRNP specificity.

We surveyed for autoantibodies to the U small nuclear ribonucleoproteins (snRNPs) in sera from 1171 patients with various connective tissue diseases by immunoprecipitation assay. We found serum, termed LaJ, which principally recognized the U5 snRNP from one patient with systemic sclerosis-polymyositis overlap syndrome. Anti-LaJ serum immunoprecipitated predominantly U5 snRNA from a 32PO4-labeled HeLa cell extract and at least five U5-specific proteins as well as the Sm core proteins from a [35S]methionine-labeled extract. Anti-LaJ serum immunoprecipitated both U5 snRNA and these five proteins in identical fractions at 15-20S by parallel sucrose gradient, suggesting physical association of these two components. Thus, we concluded that anti-LaJ serum contained antibody specific to the U5 snRNP. Antibodies specific to U5 snRNP were found in a single serum; in contrast, the prevalence of anti-U1 snRNP and anti-Sm antibody was considerably higher. Thus, the specific proteins of the U5 snRNP are rare targets for autoantibodies in patients with connective tissue disease.