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Translational control at the initiation step has been recognized as a major and important regulatory mechanism of gene expression. eIF3a, a putative subunit of eIF3 complex, has recently been shown to play an important role in regulating translation of a subset of mRNAs and found to correlate with prognosis of cancers. In this study, using nasopharyngeal carcinoma (NPC) cells as a model system we tested the hypothesis that eIF3a negatively regulates synthesis of nucleotide excision repair (NER) proteins and, thus, NER activities and cellular response to treatments with DNA damaging agents such as cisplatin. We found that a cisplatin-sensitive subclone S16 isolated from a NPC cell line CNE2 via limited dilution has increased eIF3a expression. Knocking down its expression in S16 cells increased cellular resistance to cisplatin, NER activity, and synthesis of NER proteins XPA, XPC, RAD23B, and RPA32. Altering eIF3a expression also changed cellular response to cisplatin and UV treatment in other NPC cell lines. Taken together, we conclude that eIF3a plays an important role in cisplatin response and NER activity of nasopharyngeal carcinomas by suppressing synthesis of NER proteins.

Passive immunotherapy with monoclonal antibodies (mAbs) is an efficacious treatment for Ebola virus (EBOV) infections in animal models and humans. Understanding what constitutes a protective response is critical for the development of novel therapeutic strategies. We generated an EBOV-glycoprotein-pseudotyped Human immunodeficiency virus to develop sensitive neutralizing and antibody-dependent cellular cytotoxicity (ADCC) assays as well as a bioluminescent-imaging-based mouse infection model that does not require biosafety level 4 containment. The in vivo treatment efficiencies of three novel anti-EBOV mAbs at 12 h post-infection correlated with their in vitro anti-EBOV ADCC activities, without neutralizing activity. When they were treated with these mAbs, natural killer cell (NK)-deficient mice had lower viral clearance than WT mice, indicating that the anti-EBOV mechanism of the ADCC activity of these mAbs is predominantly mediated by NK cells. One potent anti-EBOV mAb (M318) displayed unprecedented neutralizing and ADCC activities (neutralization IC50, 0.018 μg/ml; ADCC EC50, 0.095 μg/ml). These results have important implications for the efficacy of antiviral drugs and vaccines as well as for pathogenicity studies of EBOV.

Fatty acid synthase (FASN), the sole cytosolic mammalian enzyme for de novo lipid synthesis, is crucial for cancer cell survival and associates with poor prognosis. FASN overexpression has been found to cause resistance to genotoxic insults. Here we tested the hypothesis that FASN regulates DNA repair to facilitate survival against genotoxic insults and found that FASN suppresses NF-κB but increases specificity protein 1 (SP1) expression. NF-κB and SP1 bind to a composite element in the poly(ADP-ribose) polymerase 1 (PARP-1) promoter in a mutually exclusive manner and regulate PARP-1 expression. Up-regulation of PARP-1 by FASN in turn increases Ku protein recruitment and DNA repair. Furthermore, lipid deprivation suppresses SP1 expression, which is able to be rescued by palmitate supplementation. However, lipid deprivation or palmitate supplementation has no effect on NF-κB expression. Thus, FASN may regulate NF-κB and SP1 expression using different mechanisms. Altogether, we conclude that FASN regulates cellular response against genotoxic insults by up-regulating PARP-1 and DNA repair via NF-κB and SP1.fatty acid synthase | transcription regulation | DNA repair | drug resistance | radiation resistance F atty acid synthase (FASN) is the key mammalian enzyme required for de novo synthesis of palmitate. FASN expression and activity are largely suppressed by sufficient dietary fat in most normal nonadipose tissues but are abnormally elevated in many human cancers and associated with poor prognosis (1). FASN association with poor prognosis may derive in part from FASN function in drug resistance during chemotherapy. Indeed, it has been found that FASN expression and/or activity was increased in drug-selected and -resistant breast (2) and pancreatic (3) cancer cells. It was also found that FASN overexpression causes cellular resistance to DNA-damaging drugs such as doxorubicin and mitoxantrone but not to microtubule modulators such as vinblastine and paclitaxel (4). Decreased ceramide production following doxorubicin treatment via suppression of tumor necrosis factor (TNF)-α production is believed to be one of the mechanisms of FASN-induced resistance to doxorubicin (4).The observation that FASN increases resistance to genotoxic drugs prompted us to hypothesize that FASN overexpression may up-regulate DNA damage response/repair pathways. In this study, we tested this hypothesis with a focus on the repair of DNA double-strand breaks (DSBs), which are commonly induced by the anticancer drugs doxorubicin and mitoxantrone and ionizing radiation. In mammalian cells, DSBs are repaired mainly via homologous recombination (HR) and nonhomologous end-joining (NHEJ) pathways. NHEJ is the predominant form of DSB repair because it occurs during all phases of the cell cycle whereas HR only initiates at late G1 and S phases (5). Hence, we examined NHEJ repair of DSBs and found that FASN up-regulates NHEJ activity and repair of DSBs by increasing poly(ADP-ribose) polymerase 1 (PARP-1) expression via increasing the expression of spec...

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