172 research outputs found
TBP Binding-Induced Folding of the Glucocorticoid Receptor AF1 Domain Facilitates Its Interaction with Steroid Receptor Coactivator-1
The precise mechanism by which glucocorticoid receptor (GR) regulates the transcription of its target genes is largely unknown. This is, in part, due to the lack of structural and functional information about GR's N-terminal activation function domain, AF1. Like many steroid hormone receptors (SHRs), the GR AF1 exists in an intrinsically disordered (ID) conformation or an ensemble of conformers that collectively appears to be unstructured. The GR AF1 is known to recruit several coregulatory proteins, including those from the basal transcriptional machinery, e.g., TATA box binding protein (TBP) that forms the basis for the multiprotein transcription initiation complex. However, the precise mechanism of this process is unknown. We have earlier shown that conditional folding of the GR AF1 is the key for its interactions with critical coactivator proteins. We hypothesize that binding of TBP to AF1 results in the structural rearrangement of the ID AF1 domain such that its surfaces become easily accessible for interaction with other coactivators. To test this hypothesis, we determined whether TBP binding-induced structure formation in the GR AF1 facilitates its interaction with steroid receptor coactivator-1 (SRC-1), a critical coactivator that is important for GR-mediated transcriptional activity. Our data show that stoichiometric binding of TBP induces significantly higher helical content at the expense of random coil configuration in the GR AF1. Further, we found that this induced AF1 conformation facilitates its interaction with SRC-1, and subsequent AF1-mediated transcriptional activity. Our results may provide a potential mechanism through which GR and by large other SHRs may regulate the expression of the GR-target genes
Radio emission from Supernova Remnants
The explosion of a supernova releases almost instantaneously about 10^51 ergs
of mechanic energy, changing irreversibly the physical and chemical properties
of large regions in the galaxies. The stellar ejecta, the nebula resulting from
the powerful shock waves, and sometimes a compact stellar remnant, constitute a
supernova remnant (SNR). They can radiate their energy across the whole
electromagnetic spectrum, but the great majority are radio sources. Almost 70
years after the first detection of radio emission coming from a SNR, great
progress has been achieved in the comprehension of their physical
characteristics and evolution. We review the present knowledge of different
aspects of radio remnants, focusing on sources of the Milky Way and the
Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief
overview of theoretical background, analyze morphology and polarization
properties, and review and critical discuss different methods applied to
determine the radio spectrum and distances. The consequences of the interaction
between the SNR shocks and the surrounding medium are examined, including the
question of whether SNRs can trigger the formation of new stars. Cases of
multispectral comparison are presented. A section is devoted to reviewing
recent results of radio SNRs in the Magellanic Clouds, with particular emphasis
on the radio properties of SN 1987A, an ideal laboratory to investigate
dynamical evolution of an SNR in near real time. The review concludes with a
summary of issues on radio SNRs that deserve further study, and analyzing the
prospects for future research with the latest generation radio telescopes.Comment: Revised version. 48 pages, 15 figure
The Dijet Mass Spectrum and a Search for Quark Compositeness in bar{p}p Collisions at sqrt{s} = 1.8 TeV
Using the DZero detector at the 1.8 TeV pbarp Fermilab Tevatron collider, we
have measured the inclusive dijet mass spectrum in the central pseudorapidity
region |eta_jet| < 1.0 for dijet masses greater than 200 Gev/c^2. We have also
measured the ratio of spectra sigma(|eta_jet| < 0.5)/sigma(0.5 < |eta_jet| <
1.0). The order alpha_s^3 QCD predictions are in good agreement with the data
and we rule out models of quark compositeness with a contact interaction scale
< 2.4 TeV at the 95% confidence level.Comment: 11 pages, 4 figures, 2 tables, submitted to Phys. Rev. Let
Search for High Mass Photon Pairs in p-pbar --> gamma-gamma-jet-jet Events at sqrt(s)=1.8 TeV
A search has been carried out for events in the channel p-barp --> gamma
gamma jet jet. Such a signature can characterize the production of a
non-standard Higgs boson together with a W or Z boson. We refer to this
non-standard Higgs, having standard model couplings to vector bosons but no
coupling to fermions, as a "bosonic Higgs." With the requirement of two high
transverse energy photons and two jets, the diphoton mass (m(gamma gamma))
distribution is consistent with expected background. A 90(95)% C.L. upper limit
on the cross section as a function of mass is calculated, ranging from
0.60(0.80) pb for m(gamma gamma) = 65 GeV/c^2 to 0.26(0.34) pb for m(gamma
gamma) = 150 GeV/c^2, corresponding to a 95% C.L. lower limit on the mass of a
bosonic Higgs of 78.5 GeV/c^2.Comment: 9 pages, 3 figures. Replacement has new H->gamma gamma branching
ratios and corresponding new mass limit
Limits on WWZ and WW\gamma couplings from p\bar{p}\to e\nu jj X events at \sqrt{s} = 1.8 TeV
We present limits on anomalous WWZ and WW-gamma couplings from a search for
WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p
-> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron
Collider during the 1992-1995 run. The data sample corresponds to an integrated
luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling
parameters, the 95% CL limits on the CP-conserving couplings are
-0.33<lambda<0.36 (Delta-kappa=0) and -0.43<Delta-kappa<0.59 (lambda=0), for a
form factor scale Lambda = 2.0 TeV. Limits based on other assumptions are also
presented.Comment: 11 pages, 2 figures, 2 table
Search For Heavy Pointlike Dirac Monopoles
We have searched for central production of a pair of photons with high
transverse energies in collisions at TeV using of data collected with the D\O detector at the Fermilab Tevatron in
1994--1996. If they exist, virtual heavy pointlike Dirac monopoles could
rescatter pairs of nearly real photons into this final state via a box diagram.
We observe no excess of events above background, and set lower 95% C.L. limits
of on the mass of a spin 0, 1/2, or 1 Dirac
monopole.Comment: 12 pages, 4 figure
Probing Hard Color-Singlet Exchange in ppbar Collisions at root-s=630 GeV and 1800 GeV
We present results on dijet production via hard color-singlet exchange in
proton-antiproton collisions at root-s = 630 GeV and 1800 GeV using the DZero
detector. The fraction of dijet events produced via color-singlet exchange is
measured as a function of jet transverse energy, separation in pseudorapidity
between the two highest transverse energy jets, and proton-antiproton
center-of-mass energy. The results are consistent with a color-singlet fraction
that increases with an increasing fraction of quark-initiated processes and
inconsistent with two-gluon models for the hard color-singlet.Comment: 16 pages, 6 figure
Zgamma Production in pbarp Collisions at sqrt(s)=1.8 TeV and Limits on Anomalous ZZgamma and Zgammagamma Couplings
We present a study of Z +gamma + X production in p-bar p collisions at
sqrt{S}=1.8 TeV from 97 (87) pb^{-1} of data collected in the eegamma
(mumugamma) decay channel with the D0 detector at Fermilab. The event yield and
kinematic characteristics are consistent with the Standard Model predictions.
We obtain limits on anomalous ZZgamma and Zgammagamma couplings for form factor
scales Lambda = 500 GeV and Lambda = 750 GeV. Combining this analysis with our
previous results yields 95% CL limits |h{Z}_{30}| < 0.36, |h{Z}_{40}| < 0.05,
|h{gamma}_{30}| < 0.37, and |h{gamma}_{40}| < 0.05 for a form factor scale
Lambda=750 GeV.Comment: 17 Pages including 2 Figures. Submitted to PR
A Measurement of the W Boson Mass
We report a measurement of the W boson mass based on an integrated luminosity
of 82 pb from \ppbar collisions at TeV recorded in
1994--1995 by the \Dzero detector at the Fermilab Tevatron. We identify W
bosons by their decays to and extract the mass by fitting the transverse
mass spectrum from 28,323 W boson candidates. A sample of 3,563 dielectron
events, mostly due to Z to ee decays, constrains models of W boson production
and the detector. We measure \mw=80.44\pm0.10(stat)\pm0.07(syst)~GeV. By
combining this measurement with our result from the 1992--1993 data set, we
obtain \mw=80.43\pm0.11 GeV.Comment: 11 pages, 5 figure
Risk Factors for Breast Cancer and Expression of Insulin-Like Growth Factor-2 (IGF-2) in Women with Breast Cancer in Wuhan City, China
PURPOSE: The purpose of this study was to explore the risk factors for breast cancer and establish the expression rate of IGF-2 in female patients. METHODS: A case control study with 500 people in case group and 500 people in control group. A self-administered questionnaire was used to investigate risk factors for breast cancer. All cases were interviewed during a household survey. Immune-histochemical method was used to inspect the expression of IGF-2 in different tissues (benign breast lesions, breast cancer and tumor-adjacent tissue). RESULTS: Multivariate adjusted odds ratios and 95% confidence intervals were calculated using unconditional logistic regression. High body mass index (OR = 1.012,95%CI = 1.008-1.016), working attributes (OR = 1.004, 95%CI = 1.002 = 1.006), long menstrual period (OR = 1.007, 95%CI = 1.005-1.009), high parity OR = 1.003, 95%CI = 1.001-1.005) , frequent artificial abortion (OR = 1.004, 95%CI = 1.001-1.005), family history of cancer (OR = 1.003, 95%CI = 1.000-1.005), period of night shift (OR = 1.003, 95%CI = 1.001-1.006), live in high risk environment (OR = 1.005, 95%CI = 1.002-1.008), and family problems (OR = 1.010, 95%CI = 1.005-1.014) were associated with increased risk for breast cancer. In this study, good sleeping status, positive coping strategies, subjective support, and utility degree of social support were associated with reduced risk for breast cancer (OR = 0.998, 0.997, 0.985, 0.998 respectively; 95%CI = 0.996-1.000, 0.994-1.000, 0.980-0.989, 0.996-1.000, respectively). In benign breast lesions, breast cancer and tumor-adjacent tissue, IGF-2 was mainly expressed in the cytoplasm, but its expression rate was different (p<0.05). CONCLUSIONS: The incidence of breast cancer is a common result of multiple factors. IGF-2 is involved in the development of breast cancer, and its expression varies in different tissues (benign breast lesions, breast cancer and tumor-adjacent tissue)
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