60 research outputs found
Direct m6A recognition by IMP1 underlays an alternative model of target selection for non-canonical methyl-readers
m6A methylation provides an essential layer of regulation in organismal development, and is aberrant in a range of cancers and neuro-pathologies. The information encoded by m6A methylation is integrated into existing RNA regulatory networks by RNA binding proteins that recognise methylated sites, the m6A readers. m6A readers include a well-characterised class of dedicated proteins, the YTH proteins, as well as a broader group of multi-functional regulators where recognition of m6A is only partially understood. Molecular insight in this recognition is essential to build a mechanistic understanding of global m6A regulation. In this study, we show that the reader IMP1 recognises the m6A using a dedicated hydrophobic platform that assembles on the methyl moiety, creating a stable high-affinity interaction. This recognition is conserved across evolution and independent from the underlying sequence context but is layered upon the strong sequence specificity of IMP1 for GGAC RNA. This leads us to propose a concept for m6A regulation where methylation plays a context-dependent role in the recognition of selected IMP1 targets that is dependent on the cellular concentration of available IMP1, differing from that observed for the YTH proteins
HIV-1 capsid is involved in post-nuclear entry steps
BACKGROUND: HIV-1 capsid influences viral uncoating and nuclear import. Some capsid is detected in the nucleus but it is unclear if it has any function. We reported that the antibiotic Coumermycin-A1 (C-A1) inhibits HIV-1 integration and that a capsid mutation confers resistance to C-A1, suggesting that capsid might affect post-nuclear entry steps.
RESULTS: Here we report that C-A1 inhibits HIV-1 integration in a capsid-dependent way. Using molecular docking, we identify an extended binding pocket delimited by two adjacent capsid monomers where C-A1 is predicted to bind. Isothermal titration calorimetry confirmed that C-A1 binds to hexameric capsid. Cyclosporine washout assays in Jurkat CD4+ T cells expressing engineered human TRIMCyp showed that C-A1 causes faster and greater escape from TRIMCyp restriction. Sub-cellular fractionation showed that small amounts of capsid accumulated in the nuclei of infected cells and C-A1 reduced the nuclear capsid. A105S and N74D capsid mutant viruses did not accumulate capsid in the nucleus, irrespective of C-A1 treatment. Depletion of Nup153, a nucleoporin located at the nuclear side of the nuclear pore that binds to HIV-1 capsid, made the virus less susceptible to TRIMCyp restriction, suggesting that Nup153 may help maintain some integrity of the viral core in the nucleus. Furthermore C-A1 increased binding of CPSF6, a nuclear protein, to capsid.
CONCLUSIONS: Our results indicate that capsid is involved in post-nuclear entry steps preceding integration
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Suzaku Monitoring of the Iron K Emission Line in the Type 1 Active Galactic Nucleus Ngc 5548
We present seven sequential weekly observations of NGC 5548 conducted in 2007 with the Suzaku X-ray Imaging Spectrometer (XIS) in the 0.2–12 keV band and Hard X-ray Detector (HXD) in the 10–600 keV band. The iron Kα line is well detected in all seven observations and Kβ line is also detected in four observations. In this paper, we investigate the origin of the Fe K lines using both the width of the line and the reverberation mapping method. With the co-added XIS and HXD spectra, we identify Fe Kα and Kβ line at 6.396+0.009 −0.007 keV and 7.08+0.05 −0.05 keV, respectively. The width of line obtained from the co-added spectra is 38+16 −18 eV (FWHM = 4200+1800 −2000 km s−1) which corresponds to a radius of 20+50 −10 light days, for the virial production of 1.220 × 107 M in NGC 5548. To quantitatively investigate the origin of the narrow Fe line by the reverberation mapping method, we compare the observed light curves of Fe Kα line with the predicted ones, which are obtained by convolving the continuum light curve with the transfer functions in a thin shell and an inclined disk. The best-fit result is given by the disk case with i = 30◦ which is better than a fit to a constant flux of the Fe K line at the 92.7% level (F-test). However, the results with other geometries are also acceptable (P > 50%). We find that the emitting radius obtained from the light curve is 25–37 light days, which is consistent with the radius derived from the Fe K line width. Combining the results of the line width and variation, the most likely site for the origin of the narrow iron lines is 20–40 light days away from the central engine, though other possibilities are not completely ruled out. This radius is larger than the Hβ emitting parts of the broad-line region at 6–10 light days (obtained by the simultaneous optical observation), and smaller than the inner radius of the hot dust in NGC 5548 (at about 50 light days).Astronom
DNAAF1 links heart laterality with the AAA+ ATPase RUVBL1 and ciliary intraflagellar transport
DNAAF1 (LRRC50) is a cytoplasmic protein required for dynein heavy chain assembly and cilia motility, and DNAAF1 mutations cause primary ciliary dyskinesia (PCD; MIM 613193). We describe four families with DNAAF1 mutations and complex congenital heart disease (CHD). In three families, all affected individuals have typical PCD phenotypes. However, an additional family demonstrates isolated CHD (heterotaxy) in two affected siblings, but no clinical evidence of PCD. We identified a homozygous DNAAF1 missense mutation, p.Leu191Phe, as causative for heterotaxy in this family. Genetic complementation in dnaaf1-null zebrafish embryos demonstrated the rescue of normal heart looping with wild-type human DNAAF1, but not the p.Leu191Phe variant, supporting the conserved pathogenicity of this DNAAF1 missense mutation. This observation points to a phenotypic continuum between CHD and PCD, providing new insights into the pathogenesis of isolated CHD. In further investigations of the function of DNAAF1 in dynein arm assembly, we identified interactions with members of a putative dynein arm assembly complex. These include the ciliary intraflagellar transport protein IFT88 and the AAA+ (ATPases Associated with various cellular Activities) family proteins RUVBL1 (Pontin) and RUVBL2 (Reptin). Co-localization studies support these findings, with the loss of RUVBL1 perturbing the co-localization of DNAAF1 with IFT88. We show that RUVBL1 orthologues have an asymmetric left-sided distribution at both the mouse embryonic node and the Kupffer’s vesicle in zebrafish embryos, with the latter asymmetry dependent on DNAAF1. These results suggest that DNAAF1-RUVBL1 biochemical and genetic interactions have a novel functional role in symmetry breaking and cardiac development
Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)
This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands
Localization and Broadband Follow-up of the Gravitational-wave Transient GW150914
A gravitational-wave (GW) transient was identified in data recorded by
the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)
detectors on 2015 September 14. The event, initially designated G184098
and later given the name GW150914, is described in detail elsewhere. By
prior arrangement, preliminary estimates of the time, significance, and
sky location of the event were shared with 63 teams of observers
covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths
with ground- and space-based facilities. In this Letter we describe the
low-latency analysis of the GW data and present the sky localization of
the first observed compact binary merger. We summarize the follow-up
observations reported by 25 teams via private Gamma-ray Coordinates
Network circulars, giving an overview of the participating facilities,
the GW sky localization coverage, the timeline, and depth of the
observations. As this event turned out to be a binary black hole merger,
there is little expectation of a detectable electromagnetic (EM)
signature. Nevertheless, this first broadband campaign to search for a
counterpart of an Advanced LIGO source represents a milestone and
highlights the broad capabilities of the transient astronomy community
and the observing strategies that have been developed to pursue neutron
star binary merger events. Detailed investigations of the EM data and
results of the EM follow-up campaign are being disseminated in papers by
the individual teams.
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Genetic mechanisms of dietary restriction-mediated protection against proteotoxicity in C. elegans
We sought to determine if the genes shown to be required for DR to increase lifespan are also critical for DR mediated protection against proteotoxicity. Here we report the novel finding that some of these genes, hsf-1 and skn- 1, are necessary for both DR mediated lifespan extension and protection from proteotoxicity, while other genes, pha -4 and wwp-1 play only a critical role in DR induced longevity and are dispensable for the DR protective response. Additionally, we identify potential downstream targets of this DR protective response, including components of the autophagy degradation pathwa
Human cerebral response to animal affective vocalizations
It is presently unknown whether our response to affective vocalizations is specific to those generated by humans or more universal, triggered by emotionally matched vocalizations generated by other species. Here, we used functional magnetic resonance imaging in normal participants to measure cerebral activity during auditory stimulation with affectively valenced animal vocalizations, some familiar (cats) and others not (rhesus monkeys). Positively versus negatively valenced vocalizations from cats and monkeys elicited different cerebral responses despite the participants' inability to differentiate the valence of these animal vocalizations by overt behavioural responses. Moreover, the comparison with human non-speech affective vocalizations revealed a common response to the valence in orbitofrontal cortex, a key component on the limbic system. These findings suggest that the neural mechanisms involved in processing human affective vocalizations may be recruited by heterospecific affective vocalizations at an unconscious level, supporting claims of shared emotional systems across species
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