Project description:Transcription is a major obstacle for replication fork progression and a cause of genome instability. Such instability increases in mutants with a suboptimal assembly of the nascent messenger ribonucleo-protein particle (mRNP), as THO/TREX and the NPC-associated THSC/TREX-2 complex. Here we show that yeast sac3∆ and thp1∆ cells accumulate genome-wide replication obstacles as determined by the distribution of the Rrm3 helicase. Such obstacles preferentially occur at long and highly expressed genes, to which Sac3 and its interacting partner Thp1 are preferentially bound in wild-type cells.
Project description:Ifitm3 (interferon-inducible transmembrane protein 3) was previously identified as an endosomal antiviral effector protein that blocks viral infection1-4. In analyses of gene expression data from patients with B-cell leukemia and lymphoma, we identified Ifitm3 as one of the strongest predictors of poor clinical outcome. In normal resting B-cells, Ifitm3 was minimally expressed and mainly localized in endosomes. However, engagement of the B-cell receptor (BCR) and PI3K-activation strongly induced expression of Ifitm3 and phosphorylation of its N-terminus at Y20, resulting in accumulation at the cell surface. In B-cell leukemia, oncogenic kinases induced phosphorylation at Y20, resulting in constitutive plasma membrane localization of Ifitm3. Ifitm3¯ / ¯ naïve B-cells developed at normal numbers, however, B-cell activation upon antigen encounter, germinal center formation and production of antigen-specific antibodies were compromised. Likewise, oncogenes that typically induce development of leukemia and lymphoma failed to transform Ifitm3¯ / ¯ B-cells. Conversely, a phosphomimetic mutation of Y20 induced oncogenic PI3K-signaling and initiated transformation of premalignant B-cells into overt leukemia. Functional experiments revealed a previously unrecognized function of Ifitm3 as PIP3-scaffold and central amplifier of PI3K signaling downstream of the BCR and adhesion receptors. PI3K signal-amplification depends on binding of Ifitm3 to PIP3 via two lysine residues (K83 and K104) in its conserved intracellular loop. In Ifitm3¯ / ¯ B-cells, lipid rafts were depleted of PIP3, resulting in defective expression of >60 lipid raft-associated surface receptors, which impaired BCR-signaling and cellular adhesion. We conclude that phosphorylation of IFITM3 upon Bcell antigen-encounter induces a dynamic switch from antiviral effector functions in endosomes to a PI3K-amplification loop at the cell surface. IFITM3-dependent amplification of PI3K-signaling downstream of the BCR and adhesion receptors is critical to enable rapid expansion of B-cells with high affinity to antigen. In addition, multiple oncogenes depend on IFITM3 to assemble PIP3- dependent signaling complexes and amplify PI3K-signaling for malignant transformation.
Project description:Targeting tumor-infiltrating Treg cells is an efficient way to evoke an anti-tumor immune response. How Treg cells fragility and stability are regulated remains largely unknown. IFITM3 and STAT1 are interferon-induced genes that play a positive role in the progression of tumors. Here, we showed that IFITM3-deficient Tregs blunted tumor growth by strengthening the tumor-killing response and displayed the Th1-like Treg phenotype with higher secretion of IFNγ. Mechanistically, depletion of IFITM3 enhances the translation and phosphorylation of STAT1. Conversely, the decreased IFITM3 protein and mRNA levels present in STAT1-deficient Treg cells indicate that STAT1 conversely regulates the expression of IFITM3 to form a feedback loop. Blocking the inflammatory cytokine IFNγ or directly depleting STAT1-IFITM3 axis phenocopies the restored suppressive function of TI-Tregs in the tumor model. Overall, our study demonstrates that the perturbation of TI-Tregs through IFNγ-IFITM3-STAT1 feedback is essential for anti-tumor immunity and constitutes a targetable vulnerability of cancer immunotherapy.
Project description:In this study monoclonal cell lines carrying mutations in IFITM3 gene were obtained based on WI-38 VA13 cells. To research the involvement of the IFITM3 gene in cellular response to Influenza A virus infection, original WI-38 VA13 cells and the clones with depressed IFITM3 gene activity (F3, F5, Е12) were infected with influenza A/Puerto Rico/8/1934 (H1N1) virus. RNA-seq analysis of infected cell lines after 24 h was performed on an Illumina NextSeq 500 platform. The same mock-infected cells were used as controls (0 hpi). PolyA RNA-enriched fraction was used for constructing of cDNA libraries. Differential expressed genes were identified using R package DESeq2.
Project description:The Nitroreductase NfsB (NTR) prodrug of an LSD1 inhibitor is inactive in wild-type THP1 cells, but the prodrug gets activated in the LSD1 inhibitor by the NTR in NTR-expressing THP1 cells (THP1-NTR+). Cell-type specific inhibition of LSD1 in THP1-NTR+ cells with a NTR prodrug is shown with the expression data of the two cell lines, THP1-wt and THP1-NTR+. Data for the LSD1 inhibitor and a negative control with both cell lines are included.