Linking of Antitumor trans NHC-Pt(II) Complexes to G-Quadruplex DNA Ligand for Telomeric Targeting.

G-quadruplex structures (G4) are promising anticancerous targets. A great number of small molecules targeting these structures have already been identified through biophysical methods. In cellulo, some of them are able to target either telomeric DNA and/or some sequences involved in oncogene promotors, both resulting in cancer cell death.

Locking the free-rotation of a prochiral star-shaped guest molecule inside a two-dimensional nanoporous network by introduction of chlorine atoms.

Two star-shaped triazatrinaphthylene (TrisK) derivatives form highly-organized nanoporous honeycomb networks when adsorbed at the n-tetradecane/HOPG interface. STM reveals that replacing three H-atoms by three Cl-atoms in the chemical structure of the TrisK skeleton results in locking the free-rotation of the guest molecules inside the pore of the host network as a result of symmetry breaking.

Recognition of G-quadruplex DNA by triangular star-shaped compounds: with or without side chains?

We report the synthesis of two new series of triangular aromatic platforms, either with three aminoalkyl side chains (triazatrinaphthylene series, TrisK: six compounds), or without side chains (triazoniatrinaphthylene, TrisQ). The quadruplex-DNA binding behavior of the two series, which differ essentially by the localization of the cationic charges, was evaluated by means of FRET-melting and G4-FID assays. For the trisubstituted triazatrinaphthylenes (TrisK), the length of the substituents and the presence of terminal hydrogen-bond-donor groups (NH(2)) were shown to be crucial for ensuring a high quadruplex affinity (ΔT(1/2) values of up to 20 °C at 1 μM for the best candidate, TrisK3-NH) and selectivity versus duplex DNA.

"One ring to bind them all"-part I: the efficiency of the macrocyclic scaffold for g-quadruplex DNA recognition.

Macrocyclic scaffolds are particularly attractive for designing selective G-quadruplex ligands essentially because, on one hand, they show a poor affinity for the "standard" B-DNA conformation and, on the other hand, they fit nicely with the external G-quartets of quadruplexes. Stimulated by the pioneering studies on the cationic porphyrin TMPyP4 and the natural product telomestatin, follow-up studies have developed, rapidly leading to a large diversity of macrocyclic structures with remarkable-quadruplex binding properties and biological activities. In this review we summarize the current state of the art in detailing the three main categories of quadruplex-binding macrocycles described so far (telomestatin-like polyheteroarenes, porphyrins and derivatives, polyammonium cyclophanes), and in addressing both synthetic issues and biological aspects.

"One Ring to Bind Them All"-Part II: Identification of Promising G-Quadruplex Ligands by Screening of Cyclophane-Type Macrocycles.

A collection of 26 polyammonium cyclophane-type macrocycles with a large structural diversity has been screened for G-quadruplex recognition. A two-step selection procedure based on the FRET-melting assay was carried out enabling identification of macrocycles of high affinity (DeltaT(1/2) up to 30 degrees C) and high selectivity for the human telomeric G-quadruplex. The four selected hits possess sophisticated architectures, more particularly the presence of a pendant side-arm as well as the existence of a particular topological arrangement appear to be strong determinants of quadruplex binding.

Exclusive platination of loop adenines in the human telomeric G-quadruplex.

The present article reports on the platination of the human telomeric G-quadruplex by three Pt-terpyridine complexes. It is shown that extension of the aromatic surface of the terpyridine moiety surrounding the platinum atom influences both the binding affinity and the platination activity. Remarkably, the most strongly bound complex Pt-ttpy coordinates exclusively the adenine nucleobases present in the loop of the G-quadruplex.

Ligands playing musical chairs with G-quadruplex DNA: a rapid and simple displacement assay for identifying selective G-quadruplex binders.

We report here the details of G4-FID (G-quadruplex fluorescent intercalator displacement), a simple method aiming at evaluating quadruplex-DNA binding affinity and quadruplex- over duplex-DNA selectivity of putative ligands. This assay is based on the loss of fluorescence upon displacement of thiazole orange from quadruplex- and duplex-DNA matrices. The original protocol was tested using various quadruplex- and duplex-DNA targets, and with a wide panel of G-quadruplex ligands belonging to different families (i.

A hitchhiker's guide to G-quadruplex ligands.

Over the past decade, nucleic acid chemists have seen the spectacular emergence of molecules designed to interact efficiently and selectively with a peculiar DNA structure named G-quadruplex. Initially derived from classical DNA intercalators, these G-quadruplex ligands progressively became the focal point of new excitement since they appear to inhibit selectively the growth of cancer cells thereby opening interesting perspectives towards the development of novel anti-cancer drugs. The present article aims to help researchers enter this exciting research field, and to highlight recent advances in the design of G-quadruplex ligands.

Thiazole orange: a useful probe for fluorescence sensing of G-quadruplex-ligand interactions.

Fluorimetric titrations were performed to gain insight into parameters that govern the association of thiazole orange (TO) and G-quadruplex-DNA (G4-DNA). Use of loop-containing and loop-lacking quadruplexes evidenced the critical influence of the loops on the stoichiometry of the association and on the fluorescence exaltation of TO. We subsequently tried to benefit from this sensitivity to evaluate the influence of G4-DNA cationic environment on ligand binding via a recently reported G4-FID assay.

The importance of metal geometry in the recognition of G-quadruplex-DNA by metal-terpyridine complexes.

A family of terpyridine metallo-organic complexes has been designed and its recognition properties of G-quadruplex-DNA investigated. The series combines easy synthetic access and good affinity-selectivity ratio for quadruplex-DNA. Our study also highlights that the geometry of the metal center strongly governs the ability of the compounds to discriminate quadruplex from duplex-DNA.

A platinum-quinacridine hybrid as a G-quadruplex ligand.

A novel platinum-quinacridine hybrid, comprising a monofunctional Pt moiety and a G-quadruplex ligand (mono-para-quinacridine or MPQ), has been synthesized and shown to interact with quadruplex DNA via a dual noncovalent/covalent binding mode. Denaturing gel electrophoresis was used to separate the various platination products of 22AG (an oligonucleotide that mimics the human telomeric repeat) by Pt-MPQ, and it was shown that two platinated adducts are highly stable quadruplex structures. Dimethylsulfate/piperidine treatment and 3'-exonuclease digestion of the isolated adducts allowed us to precisely determine the platination pattern of 22AG by Pt-MPQ, which displays three main sites G2, G10 and G22.

Random AT library: autonomously replicating sequence (ARS) activity of chemically synthesized random sequences for transformation of nonconventional yeast species.

In a search for sequences that confer on bacterial plasmids the capacity of autonomous replication in yeast cells, we chemically synthesized polynucleotides 80 bp in length from an equimolar mixture of A and T. The random AT-polymer population, W80, was inserted into the plasmid YIp5-Kan1 (which carries the markers URA3 and G418(R), but does not replicate in yeast) and amplified in Escherichia coli. This library, representing 10 000 different AT sequences, was transformed into three species of yeast: Saccharomyces cerevisiae, Kluyveromyces lactis and Torulaspora delbrueckii.

Efficient laser operation of an Yb:S-FAP crystal at 985 nm.

We have obtained three-level cw laser operation at 985 nm with a Yb-doped S-FAP bulk crystal pumped by a Ti:sapphire laser. An output power of 250 mW for an incident pump power of 1.45 W has been achieved, which is the highest cw output power ever obtained, to our knowledge, at this wavelength with a Yb-doped crystal.

Continuous-wave diode-pumped solid-state laser with an intracavity fiber Bragg grating.

We demonstrate the feasibility of a new concept of laser that benefits from both fiber and laser crystals: a cw diode-pumped solid-state laser with an intracavity fiber Bragg grating as the output coupler. The design of the laser cavity and the experimental demonstration are both described. Several applications are mentioned.

Secretion of human proteins from yeast: stimulation by duplication of polyubiquitin and protein disulfide isomerase genes in Kluyveromyces lactis.

The efficiency of secreted production of mammalian proteins from yeasts remains unpredictably variable, depending on each protein. On the hypothesis that the control of protein conformation during protein translocation is the bottleneck in many cases, we examined the effects of an increased dosage of the genes coding for protein disulfide isomerase and of polyubiquitin on the secretion of two human proteins, serumalbumin and interleukin 1 beta. The yeast Kluyveromyces lactis was used as a production host.

The ubiquitin-encoding genes of Kluyveromyces lactis.

The ubiquitin encoding genes of Kluyveromyces lactis were cloned. Three genes, KlUBI1, KlUBI3 and KlUBI4, were found in this yeast, while in Saccharomyces cerevisiae there are four genes, UBI1, -2, -3 and -4. The UBI1/UBI2 duplication is thus absent from the K.

Protein disulphide isomerase genes of Kluyveromyces lactis.

Two genes of Kluyveromyces lactis, KlPDI1 and KlMPD1, were studied. They code for a protein disulphide isomerase and its structural and functional homologue, respectively. The KlPDI1 product was 52.

Linear DNA plasmid pPK2 of Pichia kluyveri: distinction between cytoplasmic and mitochondrial linear plasmids in yeasts.

The linear plasmids frequently found in plants and filamentous fungi are associated with mitochondria or chloroplasts. In contrast, all the linear plasmids known in yeasts are cytoplasmic elements. From a strain of the yeast Pichia kluyveri, we have isolated a new linear plasmid, pPK2, which was found to be associated with mitochondria.

A circular plasmid from the yeast Torulaspora delbrueckii.

A new member of the 2-micron family of plasmids, named pTD1, was found in the yeast Torulaspora delbrueckii, a widespread yeast associated with food. Nucleotide sequences revealed the presence of a pair of inverted repeats and three open reading frames, one of which is a homologue of the FLP recombinase gene of 2-micron plasmid. An ARS region was identified, by replication in Saccharomyces cerevisiae and T.

Linear DNA plasmids of yeasts.

Linear DNA plasmids are common among filamentous fungi and plants in which they are generally associated with mitochondria. In contrast, the linear DNA plasmids of yeast appear to be cytoplasmic and to have a specific genetic organization. In these respects the yeast linear plasmids can be regarded as a separate group of plasmids.

Linear mitochondrial DNAs from yeasts: telomeres with large tandem repetitions.

The terminal structure of the linear mitochondrial DNA (mtDNA) from the yeast Candida parapsilosis was investigated. This mtDNA, 30 kb long, has symmetrical ends forming inverted terminal repeats. These repeats are made up of a variable number of tandemly repeating units of 738 bp each; the terminal nucleotide corresponds to a precise position within the last repeat unit sequence.

NADH dehydrogenase subunit genes in the mitochondrial DNA of yeasts.

The genes encoding the NADH dehydrogenase subunits of respiratory complex I have not been identified so far in the mitochondrial DNA (mtDNA) of yeasts. In the linear mtDNA of Candida parapsilosis, we found six new open reading frames whose sequences were unambiguously homologous to those of the genes known to code for NADH dehydrogenase subunit proteins of different organisms, i.e.

Linear DNA plasmids from Pichia etchellsii, Debaryomyces hansenii and Wingea robertsiae.

Linear DNA plasmids were found in the following yeasts: four strains of Kluyveromyces lactis, one of Debaryomyces hansenii, one of Wingea robertsiae and four of Pichia etchellsii. In each case, the plasmids were present as a pair of DNA molecules of different sizes. The plasmids of K.