58 research outputs found
RNA recognition by Npl3p reveals U2 snRNA-binding compatible with a chaperone role during splicing
The conserved SR-like protein Npl3 promotes splicing of diverse pre-mRNAs. However, the RNA sequence(s) recognized by the RNA Recognition Motifs (RRM1 & RRM2) of Npl3 during the splicing reaction remain elusive. Here, we developed a split-iCRAC approach in yeast to uncover the consensus sequence bound to each RRM. High-resolution NMR structures show that RRM2 recognizes a 5´-GNGG-3´ motif leading to an unusual mille-feuille topology. These structures also reveal how RRM1 preferentially interacts with a CC-dinucleotide upstream of this motif, and how the inter-RRM linker and the region C-terminal to RRM2 contribute to cooperative RNA-binding. Structure-guided functional studies show that Npl3 genetically interacts with U2 snRNP specific factors and we provide evidence that Npl3 melts U2 snRNA stem-loop I, a prerequisite for U2/U6 duplex formation within the catalytic center of the B spliceosomal complex. Thus, our findings suggest an unanticipated RNA chaperoning role for Npl3 during spliceosome active site formation
Slitless spectrophotometry with forward modelling: principles and application to atmospheric transmission measurement
In the next decade, many optical surveys will aim to tackle the question of
dark energy nature, measuring its equation of state parameter at the permil
level. This requires trusting the photometric calibration of the survey with a
precision never reached so far, controlling many sources of systematic
uncertainties. The measurement of the on-site atmospheric transmission for each
exposure, or on average for each season or for the full survey, can help reach
the permil precision for magnitudes. This work aims at proving the ability to
use slitless spectroscopy for standard star spectrophotometry and its use to
monitor on-site atmospheric transmission as needed, for example, by the Vera C.
Rubin Observatory Legacy Survey of Space and Time supernova cosmology program.
We fully deal with the case of a disperser in the filter wheel, which is the
configuration chosen in the Rubin Auxiliary Telescope. The theoretical basis of
slitless spectrophotometry is at the heart of our forward model approach to
extract spectroscopic information from slitless data. We developed a publicly
available software called Spectractor (https://github.com/LSSTDESC/Spectractor)
that implements each ingredient of the model and finally performs a fit of a
spectrogram model directly on image data to get the spectrum. We show on
simulations that our model allows us to understand the structure of
spectrophotometric exposures. We also demonstrate its use on real data, solving
specific issues and illustrating how our procedure allows the improvement of
the model describing the data. Finally, we discuss how this approach can be
used to directly extract atmospheric transmission parameters from data and thus
provide the base for on-site atmosphere monitoring. We show the efficiency of
the procedure on simulations and test it on the limited data set available.Comment: 30 pages, 36 figures, submitted to Astronomy and Astrophysic
40S hnRNP particles are a novel class of nuclear biomolecular condensates.
Heterogenous nuclear ribonucleoproteins (hnRNPs) are abundant proteins implicated in various steps of RNA processing that assemble on nuclear RNA into larger complexes termed 40S hnRNP particles. Despite their initial discovery 55 years ago, our understanding of these intriguing macromolecular assemblies remains limited. Here, we report the biochemical purification of native 40S hnRNP particles and the determination of their complete protein composition by label-free quantitative mass spectrometry, identifying A-group and C-group hnRNPs as the major protein constituents. Isolated 40S hnRNP particles dissociate upon RNA digestion and can be reconstituted in vitro on defined RNAs in the presence of the individual protein components, demonstrating a scaffolding role for RNA in nucleating particle formation. Finally, we revealed their nanometer scale, condensate-like nature, promoted by intrinsically disordered regions of A-group hnRNPs. Collectively, we identify nuclear 40S hnRNP particles as novel dynamic biomolecular condensates
Quantum control of a cat-qubit with bit-flip times exceeding ten seconds
Binary classical information is routinely encoded in the two metastable
states of a dynamical system. Since these states may exhibit macroscopic
lifetimes, the encoded information inherits a strong protection against
bit-flips. A recent qubit - the cat-qubit - is encoded in the manifold of
metastable states of a quantum dynamical system, thereby acquiring bit-flip
protection. An outstanding challenge is to gain quantum control over such a
system without breaking its protection. If this challenge is met, significant
shortcuts in hardware overhead are forecast for quantum computing. In this
experiment, we implement a cat-qubit with bit-flip times exceeding ten seconds.
This is a four order of magnitude improvement over previous cat-qubit
implementations, and six orders of magnitude enhancement over the single photon
lifetime that compose this dynamical qubit. This was achieved by introducing a
quantum tomography protocol that does not break bit-flip protection. We prepare
and image quantum superposition states, and measure phase-flip times above 490
nanoseconds. Most importantly, we control the phase of these superpositions
while maintaining the bit-flip time above ten seconds. This work demonstrates
quantum operations that preserve macroscopic bit-flip times, a necessary step
to scale these dynamical qubits into fully protected hardware-efficient
architectures
Clonal Groupings in Serogroup X Neisseria meningitidis
The genetic diversity of 134 serogroup X Neisseria meningitis isolates from Africa, Europe, and North America was analyzed by multilocus sequence typing and pulsed-field gel electrophoresis. Although most European and American isolates were highly diverse, one clonal grouping was identified in sporadic disease and carrier strains isolated over the last 2 decades in the United Kingdom, the Netherlands, Germany, and the United States. In contrast to the diversity in the European and American isolates, most carrier and disease isolates recovered during the last 30 years in countries in the African meningitis belt belonged to a second clonal grouping. During the last decade, these bacteria have caused meningitis outbreaks in Niger and Ghana. These results support the development of a comprehensive conjugate vaccine that would include serogroup X polysaccharide
Déterminants structuraux de la reconnaissance spécifique de l'ADN par le domaine THAP de hTHAP1 et implications dans la dystonie DYT6
TOULOUSE3-BU Sciences (315552104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF
Transition-Metal-Catalyzed Uninterrupted Four-Step Sequence to Access Trisubstituted Isoxazoles
International audienceWe describe herein a novel uninterrupted four-step sequence to access trisubstituted isoxazoles from readily available propargylic alcohols using sequentially iron and palladium catalytic systems. The advantages of such a strategy are illustrated by the high overall yields and the time-saving procedure that are reported
- …