A STAT3-inhibitory hairpin decoy oligodeoxynucleotide discriminates between STAT1 and STAT3 and induces death in a human colon carcinoma cell line

<p>Abstract</p> <p>Background</p> <p>The Signal Transducer and Activator of Transcription 3 (STAT3) is activated in tumor cells, and STAT3-inhibitors are able to induce the death of those cells. Decoy oligodeoxynucleotides (dODNs), which bind to the DNA Binding Domain (DBD) of STAT3, are efficient inhibitors. However, they also inhibit STAT1, whose activity is essential not only to resistance to pathogens, but also to cell growth inhibition and programmed cell death processes. The aim of this study was to design STAT3-specific dODNs which do not affect STAT1-mediated processes.</p> <p>Results</p> <p>New dODNs with a hairpin (hpdODNs) were designed. Modifications were introduced, based on the comparison of STAT3- and STAT1-DBD interactions with DNA using 3D structural analyses. The designed hpdODNs were tested for their ability to inhibit STAT3 but not STAT1 by determining: i) cell death in the active STAT3-dependent SW480 colon carcinoma cell line, ii) absence of inhibition of interferon (IFN) γ-dependent cell death, iii) expression of STAT1 targets, and iv) nuclear location of STAT3 and STAT1. One hpdODN was found to efficiently induce the death of SW480 cells without interfering with IFNγ-activated STAT1. This hpdODN was found in a complex with STAT3 but not with STAT1 using an original in-cell pull-down assay; this hpdODN also did not inhibit IFNγ-induced STAT1 phosphorylation, nor did it inhibit the expression of the STAT1-target IRF1. Furthermore, it prevented the nuclear transfer of STAT3 but not that of IFNγ-activated STAT1.</p> <p>Conclusions</p> <p>Comparative analyses at the atomic level revealed slight differences in STAT3 and STAT1 DBDs' interaction with their DNA target. These were sufficient to design a new discriminating hpdODN that inhibits STAT3 and not STAT1, thereby inducing tumor cell death without interfering with STAT1-dependent processes. Preferential interaction with STAT3 depends on oligodeoxynucleotide sequence modifications but might also result from DNA shape changes, known to modulate protein/DNA interactions. The finding of a STAT3-specific hpdODN establishes the first rational basis for designing STAT3 DBD-specific inhibitors.</p

Solution conformation of an RNA–DNA hybrid duplex containing a pyrimidine RNA strand and a purine DNA strand

International audienceRNA–DNA hybrid duplexes are involved in transcription, replication and reverse transcription of nucleic acids. Informationon such duplexes may shed some light on the mechanism of these processes. For this purpose, the influence of base compositionon the structure of a polypyrimidine–polypurine RNA–DNA duplex r(cucuccuucucuu). d(GAGAGGAAGAGAA) has beenstudied using 1H, 31P and 13C NMR experiments, molecular modeling (JUMNA program) and NOE back-calculation methods.The resulting structure of the 13-mer hybrid duplex shows that the RNA strand is in the expected A-type conformation while theDNA strand is in a very flexible conformation. In the DNA strand, the desoxyribose sugars retain the C2%-endo B-typeconformation. The duplex helical parameters (such as inclination, twist and displacement of the bases) are close to the A-typeconformation. No bending was observed for the global axis curvature. The major groove width is close to the B-form value andthe minor groove width is intermediate between standard values for A and B-forms. These results are in favour of theindependence of minor groove size (where RNase H interacts) and the base composition of the hybrid duplexes. © 2001 ElsevierScience B.V. All rights reserved

Current Awareness

International audienceIn order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of NMR in biomedicine. Each bibliography is divided into 9 sections: 1 Books, Reviews ' Symposia; 2 General; 3 Technology; 4 Brain and Nerves; 5 Neuropathology; 6 Cancer; 7 Cardiac, Vascular and Respiratory Systems; 8 Liver, Kidney and Other Organs; 9 Muscle and Orthopaedic. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted

Structure-function analysis of the antiangiogenic ATWLPPR peptide inhibiting VEGF165 binding to neuropilin-1 and molecular dynamics simulations of the ATWLPPR/neuropilin-1 complex

1 - ArticleHeptapeptide ATWLPPR (A7R), identified in our laboratory by screening a mutated phage library, was shown to bind specifically to neuropilin-1 (NRP-1) and then to selectively inhibit VEGF165 binding to this receptor. In vivo, treatment with A7R resulted in decreasing breast cancer angiogenesis and growth. The present work is focused on structural characterization of A7R. Analogs of the peptide, obtained by substitution of each amino acid with alanine (alanine-scanning) or by amino acid deletion, have been systematically assayed to determine the relative importance of the side chains of each residue with respect to the inhibitory effect of A7R on VEGF165 binding to NRP-1. We show here the importance of the C-terminal sequence LPPR and particularly the key role of C-terminal arginine. In solution, A7R displays significant secondary structure of the backbone adopting an extended conformation. However, the functional groups of arginine are very flexible in the absence of NRP-1 pointing to an induced fit upon binding to the receptor. A MD trajectory of the A7R/NRP-1 complex in explicit water, based on the recent tuftsin/NRP-1 crystal structure, has revealed the hydrogen-bonding network that contributes to A7R's binding activity

L'economie du Limousin dans une periode de transitition

CNRS AR 12637 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Self-organized monolayer films of stimulus-responsive micelles

Weakly charged micelles of poly(2-(dimethylamino)ethyl methacrylate) [10% quaternized]-block-poly(2-(diethylamino)ethyl methacrylate) (10qDMA-DEA) adsorb to form a highly ordered monolayer at the mica-solution interface at pH 8.9. Rinsing with solvent at pH 9 has little effect on the adsorbed layer. Reduction of the pH to 4 results in an irreversible swelling of the thin film, in contrast to a micelle-to-unimer transition seen for the diblock in bulk solution. The resilience of the adsorbed layer opens up potential nanotechnological applications