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  • 1
    Publication Date: 2013-06-19
    Description: Rett syndrome (RTT) is an X-linked human neurodevelopmental disorder with features of autism and severe neurological dysfunction in females. RTT is caused by mutations in methyl-CpG-binding protein 2 (MeCP2), a nuclear protein that, in neurons, regulates transcription, is expressed at high levels similar to that of histones, and binds to methylated cytosines broadly across the genome. By phosphotryptic mapping, we identify three sites (S86, S274 and T308) of activity-dependent MeCP2 phosphorylation. Phosphorylation of these sites is differentially induced by neuronal activity, brain-derived neurotrophic factor, or agents that elevate the intracellular level of 3',5'-cyclic AMP (cAMP), indicating that MeCP2 may function as an epigenetic regulator of gene expression that integrates diverse signals from the environment. Here we show that the phosphorylation of T308 blocks the interaction of the repressor domain of MeCP2 with the nuclear receptor co-repressor (NCoR) complex and suppresses the ability of MeCP2 to repress transcription. In knock-in mice bearing the common human RTT missense mutation R306C, neuronal activity fails to induce MeCP2 T308 phosphorylation, suggesting that the loss of T308 phosphorylation might contribute to RTT. Consistent with this possibility, the mutation of MeCP2 T308A in mice leads to a decrease in the induction of a subset of activity-regulated genes and to RTT-like symptoms. These findings indicate that the activity-dependent phosphorylation of MeCP2 at T308 regulates the interaction of MeCP2 with the NCoR complex, and that RTT in humans may be due, in part, to the loss of activity-dependent MeCP2 T308 phosphorylation and a disruption of the phosphorylation-regulated interaction of MeCP2 with the NCoR complex.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3922283/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3922283/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ebert, Daniel H -- Gabel, Harrison W -- Robinson, Nathaniel D -- Kastan, Nathaniel R -- Hu, Linda S -- Cohen, Sonia -- Navarro, Adrija J -- Lyst, Matthew J -- Ekiert, Robert -- Bird, Adrian P -- Greenberg, Michael E -- 092076/Wellcome Trust/United Kingdom -- K08 MH090306/MH/NIMH NIH HHS/ -- K08MH90306/MH/NIMH NIH HHS/ -- P30 HD018655/HD/NICHD NIH HHS/ -- P30-HD 18655/HD/NICHD NIH HHS/ -- R01 NS048276/NS/NINDS NIH HHS/ -- R01NS048276/NS/NINDS NIH HHS/ -- T32 GM007753/GM/NIGMS NIH HHS/ -- England -- Nature. 2013 Jul 18;499(7458):341-5. doi: 10.1038/nature12348.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Harvard Medical School, and Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23770587" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cells, Cultured ; Co-Repressor Proteins/*metabolism ; Humans ; Methyl-CpG-Binding Protein 2/chemistry/genetics/*metabolism ; Mice ; Mutation ; Neurons/metabolism ; Phosphorylation ; Rett Syndrome/genetics ; Threonine/*metabolism ; Transcription, Genetic
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2013-06-30
    Description: We report on combined INTEGRAL and XMM–Newton observations of the supergiant fast X-ray transient (SFXT) IGR J16418–4532. The observations targeted the X-ray eclipse region of IGR J16418–4532's orbit with continuous INTEGRAL observations across ~25 per cent of orbital phase and two quasi-simultaneous XMM–Newton observations of length 20 and 14 ks, occurring during and just after the eclipse, respectively. An enhanced INTEGRAL emission history is provided with 19 previously unreported outbursts identified in the archival 18–60 keV data set. The XMM–Newton eclipse observation showed prominent Fe emission and a flux of 2.8  x 10 –13  erg cm –2 s –1 (0.5–10 keV). Through the comparison of the detected eclipse and post-eclipse flux, the supergiant mass-loss rate through the stellar wind was determined as M w  = 2.3–3.8  x 10 –7  M yr –1 . The post-eclipse XMM–Newton observation showed a dynamic flux evolution with signatures of the X-ray pulsation, a period of flaring activity, structured n H variations and the first ever detection of an X-ray intensity dip, or ‘off-state’, in a pulsating SFXT. Consideration is given to the origin of the X-ray dip, and we conclude that the most applicable of the current theories of X-ray dip generation is that of a transition between Compton-cooling-dominated and radiative-cooling-dominated subsonic accretion regimes within the ‘quasi-spherical’ model of wind accretion. Under this interpretation, which requires additional confirmation, the neutron star in IGR J16418–4532 possesses a magnetic field of ~10 14  G, providing tentative observational evidence of a highly magnetized neutron star in a SFXT for the first time. The implications of these results on the nature of IGR J16418–4532 itself and the wider SFXT class are discussed.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 3
    Publication Date: 2014-03-09
    Description: XMM–Newton observations of the supergiant fast X-ray transient IGR J17544–2619 are reported and placed in the context of an analysis of archival INTEGRAL /IBIS data that provide a refined estimate of the orbital period at 4.9272 ± 0.0004 d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ~15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544–2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 10 33 erg s –1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544–2619 dropped to ~4 x 10 32 erg s –1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544–2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544–2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544–2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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