Structure and Functional Analysis of the RNA- and Viral Phosphoprotein-Binding Domain of Respiratory Syncytial Virus M2-1 Protein

Respiratory syncytial virus (RSV) protein M2-1 functions as an essential transcriptional cofactor of the viral RNA-dependent RNA polymerase (RdRp) complex by increasing polymerase processivity. M2-1 is a modular RNA binding protein that also interacts with the viral phosphoprotein P, another component of the RdRp complex. These binding properties are related to the core region of M2-1 encompassing residues S58 to K177. Here we report the NMR structure of the RSV M2-158–177 core domain, which is structurally homologous to the C-terminal domain of Ebola virus VP30, a transcription co-factor sharing functional similarity with M2-1. The partial overlap of RNA and P interaction surfaces on M2-158–177, as determined by NMR, rationalizes the previously observed competitive behavior of RNA versus P. Using site-directed mutagenesis, we identified eight residues located on these surfaces that are critical for an efficient transcription activity of the RdRp complex. Single mutations of these residues disrupted specifically either P or RNA binding to M2-1 in vitro. M2-1 recruitment to cytoplasmic inclusion bodies, which are regarded as sites of viral RNA synthesis, was impaired by mutations affecting only binding to P, but not to RNA, suggesting that M2-1 is associated to the holonucleocapsid by interacting with P. These results reveal that RNA and P binding to M2-1 can be uncoupled and that both are critical for the transcriptional antitermination function of M2-1

A comparison between observed and predicted values for the entrainment coefficient in the planetary boundary layer

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Résonance paramagnétique électronique en champ faible étude des structures hyperfines de solutions radicaliques. Applications

The theoretical considerations on paramagnetic résonance spectra in the low-field region (« π » transitions, Δm = ± 1, which are expected when the rf magnetic field is perpendicular to the static field and « σ» transitions, Δm = 0, when both fields are parallel), for one or two electrons coupled to several nuclei, monoradical or biradical in dilute solutions, are applied to some particular cases which are commonly met. First, the situation of the electron coupled to several nuclei can be explained. Secondly, these results can be applied to the identification of a monoradical or a biradical ; this identification is not always possible when paramagnetic résonance spectra of the free radical are investigated in the high-field region, for the spectra of the free monoradical and the free biradical can be the same in some cases. This theoretical study is made clear by some expérimental results: paramagnetic résonance spectra, « π » and especially « σ » transitions, of some free-monoradicals are studied here in the low field region.L'étude théorique des structures hyperfines en champ faible (transitions « π », Δm = ± 1, induites lorsque le champ radiofréquence est perpendiculaire au champ continu, et transitions « σ », Δm = 0, induites lorsque ces deux champs sont parallèles) est présentée dans les cas particuliers les plus courants pour un ou deux électrons libres couplés à plusieurs noyaux (monoradicaux ou biradicaux en solution). D'une part, elle permet l'analyse du comportement de l'électron libre dans ces conditions. D'autre part, elle suggère l'idée d'appliquer la méthode à l'identification d'un monoradical ou d'un biradical ; cette identification n'est pas toujours possible par observation des spectres de résonance paramagnétique électronique en champ fort, car ceux d'un monoradical et d'un biradical peuvent alors dans certains cas être identiques. Les résultats théoriques sont illustrés par quelques résultats expérimentaux : étude des spectres de monoradicaux observés en champ faible, transitions « π » et surtout transitions « σ »

Mouvements convectifs de la couche limite atmosphérique observée au moyen de sondeurs acoustiques Doppler et d'instruments portés par un ballon captif.

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First testing of a volcano Doppler radar (Voldorad) at Mount Etna, Italy

International audienceA medium-power (1 kW) Doppler radar of limited weight (110 kg) and working in the UHF band has been developed for active remote sensing of volcanic eruptions. Named Voldorad, this radar is designed to monitor eruptive activities of variable magnitude at medium distance range (-0.5-5 km), in any weather condition, and fills the gap between low-and high-power radar or sodar systems previously tested on volcanoes. Voldorad was operated for the first time during an eruption of Mr. Etna on October 11-12, 19911. Doppler spectra recorded at 1 km distance from the vent reveal powerful echoes during the eruption paroxysm (lava fountains), which gradually decreased along with declining activity. An average vertical velocity of 110-117 m s 4 is inferred for the eruptive jets. by Hort and Sey•ied [1998] and Sey•ied and Hort [1999] is more promising. The first tests were conducted 200-300 m away from the vent, but the operating range could be increased by using a parabolic mirror antenna with a small aperture [Seyfried and Hort, 1999]. Based on the [JHF wind profiler technique [e.g. Ecklund et al., 1990], we have developed and tested a medium-power pulsed Doppler radar specifically devoted to volcanic sounding [Dubosclard et al., 1999]. Named Voldorad, this radar can operate at medium distance (-0.5 to 5 km) from a volcanic vent and is compact enough to be easily set up on a volcano. In the following, we describe this new insreinvent and report preliminary data recorded during an eruptive sequence of Mount Etna (Sicily) in October 1998

Remotely monitoring volcanic activity with ground-based Doppler radar

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AVTIS: A novel millimetre-wave ground based instrument for volcano remote sensing

During May and June 2004, we tested a novel, millimetre-wave ground based, dual-mode radar and radiometer on Soufrière Hills Volcano, Montserrat. AVTIS (All-weather Volcano Topography Imaging Sensor) has an active (radar) mode designed to image the distance to lava domes on volcanoes whose summits are commonly obscured by persistent cloud, such as Soufrière Hills Volcano. The passive (radiometer) mode can be employed to measure the surface temperature of the imaged topography. In its current form, AVTIS can be deployed by two people and takes 50 min to acquire a 20° × 5° scene at 0.1° increments. During the fieldwork period the lava dome was not growing and only the radar mode was used. The data recorded indicate that the maximum distance imaged was about 3800 m. Combining datasets acquired from different viewpoints can potentially provide a full 3D topographic model. The accuracy and completeness of this reconstruction are reduced by two factors. Firstly, relatively small grazing angles of the ground-based line-of-sight rendered incised valleys invisible. Secondly, methods currently used to orient the instrument limit the accuracy of the resulting topographic information. Nevertheless, valuable information on new topographic surfaces was obtained in an area north of the lava dome where a valley has been infilled by deposits and in the amphitheatre created by the giant collapse event of July 2003