CpG oligodeoxynucleotide 5mer-induced apoptosis in MOLT-4 leukaemia cells does not require caspase 3 or new protein synthesis

DNA Interaction Studies of Selected Polyamine Conjugates

The interaction of polyamine conjugates with DNA double helix has been studied. Binding properties were examined by ethidium bromide (EtBr) displacement and DNA unwinding/topoisomerase I/II (Topo I/II) activity assays, as well as dsDNA thermal stability studies and circular dichroism spectroscopy. Genotoxicity of the compounds was estimated by a comet assay. It has been shown that only compound 2a can interact with dsDNA via an intercalative binding mode as it displaced EtBr from the dsDNA-dye complex, with Kapp = 4.26 × 10⁶ M-1; caused an increase in melting temperature; changed the circular dichroism spectrum of dsDNA; converted relaxed plasmid DNA into a supercoiled molecule in the presence of Topo I and reduced the amount of short oligonucleotide fragments in the comet tail. Furthermore, preliminary theoretical study has shown that interaction of the discussed compounds with dsDNA depends on molecule linker length and charge distribution over terminal aromatic chromophores.

Transcriptional analysis of apoptotic cerebellar granule neurons following rescue by gastric inhibitory polypeptide

Apoptosis triggered by exogenous or endogenous stimuli is a crucial phenomenon to determine the fate of neurons, both in physiological and in pathological conditions. Our previous study established that gastric inhibitory polypeptide (Gip) is a neurotrophic factor capable of preventing apoptosis of cerebellar granule neurons (CGNs), during its pre-commitment phase. In the present study, we conducted whole-genome expression profiling to obtain a comprehensive view of the transcriptional program underlying the rescue effect of Gip in CGNs. By using DNA microarray technology, we identified 65 genes, we named survival related genes, whose expression is significantly de-regulated following Gip treatment. The expression levels of six transcripts were confirmed by real-time quantitative polymerase chain reaction. The proteins encoded by the survival related genes are functionally grouped in the following categories: signal transduction, transcription, cell cycle, chromatin remodeling, cell death, antioxidant activity, ubiquitination, metabolism and cytoskeletal organization. Our data outline that Gip supports CGNs rescue via a molecular framework, orchestrated by a wide spectrum of gene actors, which propagate survival signals and support neuronal viability.

Oligonucleotide cyclization: the thiol-maleimide reaction revisited

A novel method to synthesize cyclic oligonucleotides (5- to 26-mer) using the thiol-maleimide reaction is described. The target molecules were obtained after subsequent removal of thiol and maleimide protecting groups from 5'-maleimido-3'-thiol-derivatized linear precursors. Retro-Diels-Alder conditions deprotecting the maleimide simultaneously promoted cyclization cleanly and in high yield.

Dz13, a c-jun DNAzyme, is a potent inducer of caspase-2 activation

Signaling pathways for caspase-2-mediated apoptosis are poorly defined. This is partially due to a lack of a reproducible stimulus to trigger caspase-2 activation. We present the oligonucleotide Dz13, a DNA enzyme that cleaves c-Jun mRNA and is capable of inhibiting various model tumors in mice, which potently induces caspase-2 resulting in apoptosis in a panel of tumor cell lines. Dz13-mediated cell death occurred even in the absence of known caspase-2 molecular partners in p53-induced protein with a death domain, RIP-associated Ich-1/CED homologous protein with death domain, or DNA-dependent protein kinase catalytic subunit, or other caspases in cell lines of breast cancer, prostate cancer, osteosarcoma, and liposarcoma. z-VDVAD-fmk, caspase-2(-/-) mouse embryonic fibroblasts and siRNA silencing of caspase-2 in tumor cells abrogated Dz13-mediated cell death. In an orthotopic tumor model, expression of caspase-2 increased as the tumor metastasized and caspase-2 expression was sporadic in patient tumor specimens. These findings provide hope that Dz13, and other agents that evoke activation of caspase-2, may be therapeutic clinically.

Enhancement of radiosensitivity by CpG-oligodeoxyribonucleotide-7909 in human non-small cell lung cancer A549 cells

CpG-oligodeoxyribonucleotides (CpG-ODNs), which induce signaling through the toll-like receptor 9, are currently under investigation as immunity stimulators against cancer. It has recently been suggested that CpG-ODNs may also enhance sensitivity to traditional therapies including chemotherapy in certain cancer-cell lines. The purpose of this study was to define the activity of CpG-ODN7909 in increasing radiosensitivity of the human non-small cell lung cancer cell line A549 in vitro. First, a dose- and time-dependent inhibitory effect on cell viability was observed after A549 cells were treated with different concentrations of CpG-ODN7909 (5, 10, 30, and 60 microg/mL). Second, decreased cell clonogenic survival, enhanced cell apoptotic index, accumulated percentage of cells in the G2/M phase, and increased tumor necrosis factor (TNF)-alpha secretion were found after combined treatments with 10 microg/mL of CpG-ODN7909 and radiation compared to either treatment alone (p < 0.05). Furthermore, the toll-like receptor 9 mRNA was found to express in A549. The results suggest that CpG-ODN7909 can increase the radiosensitivity of human non-small cell lung cancer A549 cells, which may be associated with reduced cell clonogenic survival, enhanced apoptosis, prolonged cell-cycle arrest in G2/M, and stimulation of TNF-alpha secretion.

Dz13, a DNAzyme targeting c-jun, induces off-target cytotoxicity in endothelial cells with features of nonapoptotic programmed cell death

We have previously shown that Dz13, a catalytic DNA molecule (DNAzyme) designed against c-jun, is cytotoxic to nonquiescent cells by a mechanism independent of c-jun mRNA cleavage. In this report, we evaluated programmed cell death (PCD) pathways in order to gain further insight into the mechanism of action of Dz13. Using human dermal microvascular endothelial cells (HMEC-1), we found that Dz13-mediated cell death is characterized by mitochondrial depolarization, caspase-8 activation, lysosomal increase, and autophagosome formation. Classical DNA laddering and translocation of mitochondrial proteins were not observed. An array of inhibitors, including those targeting caspases, failed to abrogate cytotoxicity and mitochondrial depolarization. Cytotoxicity did not proceed from endoplasmic reticulum (ER) stress. The possible involvement of PARP-1 in Dz13-mediated cytotoxicity was indicated by its differential release as gauged by protein extraction data and its apparent binding to Dz13, as evidenced by protein pull-down experiments. This study on Dz13-mediated cytotoxicity presents a detailed investigation into the interplay of cell death effectors involved in apoptosis, autophagy, and necrosis, and demonstrates a novel form of oligonucleotide-mediated cytotoxicity with features of PCD.

The role of potential splicing factors including RBMY, RBMX, hnRNPG-T and STAR proteins in spermatogenesis

Investigations into the RBM gene family are uncovering networks of protein interactions which regulate RNA processing, and which might operate downstream of signal transduction pathways. Similar pathways likely operate in germ cells and somatic cells, with RBMY, hnRNPGT and T-STAR proteins providing germ cell-specific components. These pathways may be important for normal germ cell development, and might be compromised in men with Y chromosome deletions affecting RBMY gene expression. The STAR proteins have multiple functions in pre-mRNA splicing, signalling and cell cycle control. These processes might have to be very finely regulated during germ cell development, which involves both two sequential meiotic divisions (meiosis I and II) as well as mitotic (spermatogonial) cell divisions, and which is controlled by paracrine signalling within the testis from Sertoli cells.