Pivotal role of the endoplasmic reticulum stress-related XBP1s/miR-22/SIRT1 axis in acute myeloid leukemia apoptosis and response to chemotherapy.

Malignant growth relies on rapid protein synthesis frequently leading to endoplasmic reticulum (ER) overload and accumulation of unfolded or misfolded protein in this cellular compartment. In the ER, protein homeostasis is finely regulated by a mechanism called the unfolded protein response (UPR), involving the activation of signalization pathways mediated by three transmembrane proteins, namely PERK, IRE1 and ATF6. IRE1 endoribonuclease activation leads in particular to the splicing of the cytosolic mRNA encoding the key UPR-specific transcription factor XBP1s.

ER Stress and Unfolded Protein Response in Leukemia: Friend, Foe, or Both?

The unfolded protein response (UPR) is an evolutionarily conserved adaptive signaling pathway triggered by a stress of the endoplasmic reticulum (ER) lumen compartment, which is initiated by the accumulation of unfolded proteins. This response, mediated by three sensors-Inositol Requiring Enzyme 1 (IRE1), Activating Transcription Factor 6 (ATF6), and Protein Kinase RNA-Like Endoplasmic Reticulum Kinase (PERK)-allows restoring protein homeostasis and maintaining cell survival. UPR represents a major cytoprotective signaling network for cancer cells, which frequently experience disturbed proteostasis owing to their rapid proliferation in an usually unfavorable microenvironment.

Translational Regulations in Response to Endoplasmic Reticulum Stress in Cancers.

During carcinogenesis, almost all the biological processes are modified in one way or another. Among these biological processes affected, anomalies in protein synthesis are common in cancers. Indeed, cancer cells are subjected to a wide range of stresses, which include physical injuries, hypoxia, nutrient starvation, as well as mitotic, oxidative or genotoxic stresses.

Are dual-purpose and male layer chickens more resilient against a low-protein-low-soybean diet than slow-growing broilers?

1. Although fattening dual-purpose types or male layer hybrid chickens appears more ethical than the common practice of culling day-old male layer chicks, the lower feed efficiency of these birds raises concerns. Replacing feed ingredients that compete with food production by those of lower value for human nutrition would be beneficial.

The PERK Branch of the Unfolded Protein Response Promotes DLL4 Expression by Activating an Alternative Translation Mechanism.

Delta-like 4 (DLL4) is a pivotal endothelium specific Notch ligand that has been shown to function as a regulating factor during physiological and pathological angiogenesis. DLL4 functions as a negative regulator of angiogenic branching and sprouting. Interestingly, is with one of the few examples of haplo-insufficiency, resulting in obvious vascular abnormalities and in embryonic lethality.

CyclinD-CDK4/6 complexes phosphorylate CDC25A and regulate its stability.

The phosphatase CDC25A is a key regulator of cell cycle progression by dephosphorylating and activating cyclin-CDK complexes. CDC25A is an unstable protein expressed from G1 until mitosis. CDC25A overexpression, which can be caused by stabilization of the protein, accelerates the G1/S and G2/M transitions, leading to genomic instability and promoting tumorigenesis.

Phosphorylation of CDC25A on SER283 in late S/G2 by CDK/cyclin complexes accelerates mitotic entry.

The Cdc25A phosphatase is an essential activator of CDK-cyclin complexes at all steps of the eukaryotic cell cycle. The activity of Cdc25A is itself regulated in part by positive and negative feedback regulatory loops performed by its CDK-cyclin substrates that occur in G1 as well as during the G1/S and G2/M transitions. However, the regulation of Cdc25A during G2 phase progression before mitotic entry has not been intensively characterized.

The hsa-miR-125a/hsa-let-7e/hsa-miR-99b cluster is potentially implicated in Cystic Fibrosis pathogenesis.

Background: Cystic Fibrosis (CF) is an autosomal recessive disorder implicating the Cystic Fibrosis Transmembrane Regulator (CFTR). Even though CF is mainly considered an inherited monogenic disease, numerous findings over the last few years argue for a more complicated multifactorial disease involving modifier genes. The 19q13.

Targeted gene silencing into solid tumors with electrically mediated siRNA delivery.

Short interfering RNAs (siRNAs) represent new potential therapeutic tools, owing to their capacity to induce strong, sequence-specific gene silencing in cells. However, their clinical development requires new, safe, and efficient in vivo siRNA delivery methods. In this study, we report an efficient in vivo approach for targeting gene knockdown in solid tumors by the use of external electric field pulses.

Spindle assembly defects leading to the formation of a monopolar mitotic apparatus.

Mitotic spindle formation in animal cells involves microtubule nucleation from two centrosomes that are positioned at opposite sides of the nucleus. Microtubules are captured by the kinetochores and stabilized. In addition, microtubules can be nucleated independently of the centrosome and stabilized by a gradient of Ran-GTP, surrounding the mitotic chromatin.

In vivo gene silencing in solid tumors by targeted electrically mediated siRNA delivery.

RNA interference (RNAi)-mediated gene silencing approaches appear very promising for therapies based on the targeted inhibition of disease-relevant genes. The major hurdle to the therapeutic development of RNAi strategies remains, however, the efficient delivery of the RNAi-inducing molecules, the short interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs), to the target tissue. With respect to cancer treatment the development of efficient delivery methods into solid tumors appears as a critical issue.

Inhibition of gene expression in mice muscle by in vivo electrically mediated siRNA delivery.

Owing to their capacity to induce strong, sequence-specific, gene silencing in cells, short interfering RNAs (siRNAs) represent new potential therapeutic tools. This development requires, however, new safe and efficient in vivo siRNA delivery methods. In the present technical report, we show that electrically mediated siRNA transfer can suppress transgene expression in adult mice muscles.

Elongation of centriolar microtubule triplets contributes to the formation of the mitotic spindle in gamma-tubulin-depleted cells.

The assembly of the mitotic spindle after depletion of the major gamma-tubulin isotype by RNA-mediated interference was assessed in the Drosophila S2 cell line. Depletion of gamma-tubulin had no significant effect on the cytoskeletal microtubules during interphase. However, it promoted an increase in the mitotic index, resulting mainly in monopolar and, to a lesser extent, asymmetrical bipolar prometaphases lacking astral microtubules.

Interconnections between E2-dependent regulation of cell cycle progression and apoptosis in MCF-7 tumors growing on nude mice.

Growth of human breast adenocarcinoma MCF-7 cells as a tumor on nude mice is dependent on estrogen. It has been shown that estrogen withdrawal (EW) induces a partial regression of the tumor via an inhibition of cell proliferation and an induction of apoptosis. We investigated in this in vivo model the underlying molecular mechanisms of the hormone-dependent regulation of cell cycle machinery and apoptosis.

Human 76p: A new member of the gamma-tubulin-associated protein family.

The role of the centrosomes in microtubule nucleation remains largely unknown at the molecular level. gamma-Tubulin and the two associated proteins h103p (hGCP2) and h104p (hGCP3) are essential. These proteins are also present in soluble complexes containing additional polypeptides.

Identification of proliferation-induced genes in Arabidopsis thaliana. Characterization of a new member of the highly evolutionarily conserved histone H2A.F/Z variant subfamily.

The changes in gene expression associated with the reinitiation of cell division and subsequent progression through the cell cycle in Arabidopsis thaliana cell-suspension cultures were investigated. Partial synchronization of cells was achieved by a technique combining phosphate starvation and a transient treatment with the DNA replication inhibitor aphidicolin. Six cDNAs corresponding to genes highly induced in proliferating cells and showing cell-cycle-regulated expression were obtained by the mRNA differential display technique.

Novel molecular markers for late phases of the growth cycle of Arabidopsis thaliana cell-suspension cultures are expressed during organ senescence.

In an Arabidopsis thaliana T87-C3 cell-suspension culture, entry into the growth-arrest phase is rapidly followed by a loss of cell viability. Three cDNA clones, SRG1, SRG2, and SRG3, corresponding to genes with transcripts that accumulate during these late phases, were isolated by the mRNA differential display method. Amino acid sequence analysis shows that the putative SRG1 protein is a new member of the Fe(II)/ascorbate oxidase superfamily, and that SRG2 codes for a protein with significant homology to beta-glucosidases.

A method for the elimination of false positives generated by the mRNA differential display technique.

The recently described mRNA differential display method provides an attractive tool for the isolation of genes showing regulated expression in a variety of systems. A key step in this technique consists of the isolation of PCR-synthesized radioactive cDNAs corresponding to differentially expressed mRNAs. Here, we show that the purified cDNAs remain contaminated with unrelated cDNA sequences that may lead to the artifactual isolation of false positives in the subsequent steps of the method.

Assaying synthetic ribozymes in plants: high-level expression of a functional hammerhead structure fails to inhibit target gene activity in transiently transformed protoplasts.

A hammerhead ribozyme designed against the mRNA coding for the Escherichia coli beta-glucuronidase (GUS) reporter enzyme was constructed. The synthetic ribozyme appeared able to correctly cleave in vitro the target RNA. This catalytic molecule was then assayed for in vivo activity in plant protoplasts.

Conserved epitopes on plant H1 histones recognized by monoclonal antibodies.

A series of monoclonal antibodies specific for distinct regions of H1 histone from the plant Nicotiana tabacum were obtained from fusion experiments with spleen cells of mice immunized with tobacco nuclear extracts. These monoclonal antibodies were characterized and the evolutionary conservation of the epitopes in higher plants and animals studied by immunoblotting and enzyme-linked immunosorbent assay (ELISA). Whereas some epitopes appear restricted to the Solanaceae plant family, others are common to all higher eukaryotes tested and even detectable on nuclear proteins of yeast.

Strand-specific viral DNA synthesis in purified viroplasms isolated from turnip leaves infected with cauliflower mosaic virus.

There is some evidence that two steps are involved in the DNA replication of cauliflower mosaic virus (CaMV): the first one may occur in the nucleus and the second one in the cytoplasm of infected cells. The latter would correspond to the reverse transcription step recently proposed in the model of the viral life cycle, and could occur in the viroplasms which are CaMV-induced cytoplasmic inclusion bodies. In order to test whether viroplasms are capable of DNA synthesis and to characterize the associated enzymatic activities, we developed an extensive purification method for these organelles.