1,136 research outputs found
Mechanisms of pathogenesis of human retroviruses : symposium
No full textMeeting: International Conference on AIDS, 5th, 4-9 June, 1989, Montreal, QC, CAPresenters: Brendan A. Larder, Paul Maddon, Bryan R. Cullen, Robert C. Gall
Gut and blood differ in constitutive blocks to HIV transcription, suggesting tissue-specific differences in the mechanisms that govern HIV latency
No full textLatently-infected CD4+ T cells are widely considered to be the major barrier to a cure for HIV. Much of our understanding of HIV latency comes from latency models and blood cells, but most HIV-infected cells reside in lymphoid tissues such as the gut. We hypothesized that tissue-specific environments may impact the mechanisms that govern HIV expression. To assess the degree to which different mechanisms inhibit HIV transcription in the gut and blood, we quantified HIV transcripts suggestive of transcriptional interference (U3-U5; "Read-through"), initiation (TAR), 5' elongation (R-U5-pre-Gag; "Long LTR"), distal transcription (Nef), completion (U3-polyA; "PolyA"), and multiple splicing (Tat-Rev) in matched peripheral blood mononuclear cells (PBMCs) and rectal biopsies, and matched FACS-sorted CD4+ T cells from blood and rectum, from two cohorts of ART-suppressed individuals. Like the PBMCs, rectal biopsies showed low levels of read-through transcripts (median = 23 copies/106 cells) and a gradient of total (679)>elongated(75)>Nef(16)>polyadenylated (11)>multiply-spliced HIV RNAs(polyadenylated>multiply-spliced transcripts, but the ratio of total to elongated transcripts was 6-fold lower than in blood CD4+ T cells (P = 0.016), suggesting less of a block to HIV transcriptional elongation in rectal CD4+ T cells. Levels of total transcripts per provirus were significantly lower in rectal biopsies compared to PBMCs (median 3.5 vs. 15.4; P = 0.008) and in sorted CD4+ T cells from rectum compared to blood (median 2.7 vs. 31.8; P = 0.016). The lower levels of HIV transcriptional initiation and of most HIV transcripts per provirus in the rectum suggest that this site may be enriched for latently-infected cells, cells in which latency is maintained by different mechanisms, or cells in a "deeper" state of latency. These are important considerations for designing therapies that aim to disrupt HIV latency in all tissue compartments.</div
SHMT2 and the BRCC36/BRISC deubiquitinase regulate HIV-1 Tat K63-ubiquitylation and destruction by autophagy
No full textHIV-1 Tat is a key regulator of viral transcription, however little is known about the mechanisms that control its turnover in T cells. Here we use a novel proteomics technique, called DiffPOP, to identify the molecular target of JIB-04, a small molecule compound that potently and selectively blocks HIV-1 Tat expression, transactivation, and virus replication in T cell lines. Mass-spectrometry analysis of whole-cell extracts from 2D10 Jurkat T cells revealed that JIB-04 targets Serine Hydroxymethyltransferase 2 (SHMT2), a regulator of glycine biosynthesis and an adaptor for the BRCC36 K63Ub-specific deubiquitinase in the BRISC complex. Importantly, knockdown of SHMT1,2 or BRCC36, or exposure of cells to JIB-04, strongly increased Tat K63Ub-dependent destruction via autophagy. Moreover, point mutation of multiple lysines in Tat, or knockdown of BRCC36 or SHMT1,2, was sufficient to prevent destruction of Tat by JIB-04. We conclude that HIV-1 Tat levels are regulated through K63Ub-selective autophagy mediated through SHMT1,2 and the BRCC36 deubiquitinase.</div
The Re-Valuation of William Jennings Bryan In Woodrow Wilson\u27s Administration
No full textThe Re-evaluation of William Jennings Bryan in Woodrow Wilson’s Administration is a study of the relationships of William Jennings Bryan, Secretary of State, Edward M. House, uncommissioned agent of Woodrow Wilson, Walter Hines Page, United States. Ambassador to England, and Woodrow Wils0n, President of the United States. The author’s purpose in writing this thesis is to throw light upon the machinations that were carried on behind the back of William Jennings Bryan, as Secretary of State in Woodrow Wilson\u27s Administration. This investigation gives to Bryan a higher and more reputable position in American history than he is usually accorded. In order to accomplish this task it was necessary to re-evaluate The Intimate Papers of Colonel House which covers the Colonel\u27s early youth up to the end of World War I. The period 1912-1915 was given special attention. The author does not contend that Bryan should have been given the appointment, nor does he contend that there were not others who could have served in the capacity of Secretary of State with more ability than Bryan. The author does contend that with all the handicaps that Bryan faced, the Commoner performed his duty to the American people admirably
Professor Bryan Harris Remembered: Volez to a Pierce Law Friend
No full textBryan Harris, MA (Oxon), passed away recently in his beloved native England, after a brief illness. His wife Mary, two sons and a daughter survive him. Bryan Harris had a long and distinguished career as an author, educator, barrister, diplomat, publisher and lobbyist. He was a consultant on European Union policies and laws to commercial and professional firms and associations. For almost three decades he was a Member of the Board of Trustees and Adjunct Professor of European Union Law at Pierce Law. Pierce Law President and Dean, John Hutson summed up what many members of the Pierce Law community expressed to me as I prepared this tribute saying, I think of Bryan mostly in single words ... jovial, cheerful, humble, dignified, diplomatic, caring ... Dean Huston shared that Professor Harris will be recognized during the 2004 Commencement
Sagittal Alignment Comparison of Bryan Disc Arthroplasty With ProDisc-C Arthroplasty A Prospective, Randomized Controlled Clinical Trial
No full textStudy Design: A prospective, randomized study of the radiographic outcomes in patients undergoing single-level cervical arthroplasty with Bryan disc and ProDisc-C prosthesis. Objective: The purpose of this trial was to compare the alignment changes of Bryan disc arthroplasty (modified techniques) with ProDisc-C arthroplasty. Summary of Background Data: Aggravation of kyphosis is the known challenge after Bryan disc arthroplasty. Both Bryan disc arthroplasty with modified techniques and ProDisc-C arthroplasty were reported to avoid the postoperative local kyphosis. There have been no studies comparing the alignment changes after Bryan disc arthroplasty with ProDisc-C arthroplasty. Methods: We conducted a randomized controlled clinical trial enrolling patients with cervical disc disease. Ultimately 20 patients received Bryan disc arthroplasty with modified surgical techniques and 26 patients received ProDisc-C arthroplasty. Functional spinal unit (FSU) and overall cervical alignment (Cobb angle of C2/7) were compared at final follow-up. Results: (1) FSU angle: the FSU angle was maintained for the Bryan disc group (from 0.8 to 0.6 degrees) without statistical significance; the FSU angle increased 2.9 degrees for the ProDisc-C group (from -0.3 to 2.6 degrees) with statistical significance. (2) Overall alignment: the overall alignments did not change for both Bryan disc and ProDisc-C groups. Conclusions: Bryan disc arthroplasty with modified techniques can maintain the lordosis of FSU, whereas ProDisc-C arthroplasty can restore the lordosis of FSU. For the patients with preoperative FSU kyphosis, ProDisc-C arthroplasty may be a better choice to restore the lordosis.Clinical NeurologyOrthopedicsSCI(E)PubMed1ARTICLE6381-3852
HIV Integration Targeting: A Pathway Involving Transportin-3 and the Nuclear Pore Protein RanBP2
No full textGenome-wide siRNA screens have identified host cell factors important for efficient HIV infection, among which are nuclear pore proteins such as RanBP2/Nup358 and the karyopherin Transportin-3/TNPO3. Analysis of the roles of these proteins in the HIV replication cycle suggested that correct trafficking through the pore may facilitate the subsequent integration step. Here we present data for coupling between these steps by demonstrating that depletion of Transportin-3 or RanBP2 altered the terminal step in early HIV replication, the selection of chromosomal sites for integration. We found that depletion of Transportin-3 and RanBP2 altered integration targeting for HIV. These knockdowns reduced HIV integration frequency in gene-dense regions and near gene-associated features, a pattern that differed from that reported for depletion of the HIV integrase binding cofactor Psip1/Ledgf/p75. MLV integration was not affected by the Transportin-3 knockdown. Using siRNA knockdowns and integration targeting analysis, we also implicated several additional nuclear proteins in proper target site selection. To map viral determinants of integration targeting, we analyzed a chimeric HIV derivative containing MLV gag, and found that the gag replacement phenocopied the Transportin-3 and RanBP2 knockdowns. Thus, our data support a model in which Gag-dependent engagement of the proper transport and nuclear pore machinery mediate trafficking of HIV complexes to sites of integration
A lysine ring in HIV capsid pores coordinates IP6 to drive mature capsid assembly.
No full textThe HIV capsid self-assembles a protective conical shell that simultaneously prevents host sensing whilst permitting the import of nucleotides to drive DNA synthesis. This is accomplished through the construction of dynamic, highly charged pores at the centre of each capsid multimer. The clustering of charges required for dNTP import is strongly destabilising and it is proposed that HIV uses the metabolite IP6 to coordinate the pore during assembly. Here we have investigated the role of inositol phosphates in coordinating a ring of positively charged lysine residues (K25) that forms at the base of the capsid pore. We show that whilst IP5, which can functionally replace IP6, engages an arginine ring (R18) at the top of the pore, the lysine ring simultaneously binds a second IP5 molecule. Dose dependent removal of K25 from the pore severely inhibits HIV infection and concomitantly prevents DNA synthesis. Cryo-tomography reveals that K25A virions have a severe assembly defect that inhibits the formation of mature capsid cones. Monitoring both the kinetics and morphology of capsids assembled in vitro reveals that while mutation K25A can still form tubes, the ability of IP6 to drive assembly of capsid cones has been lost. Finally, in single molecule TIRF microscopy experiments, capsid lattices in permeabilised K25 mutant virions are rapidly lost and cannot be stabilised by IP6. These results suggest that the coordination of IP6 by a second charged ring in mature hexamers drives the assembly of conical capsids capable of reverse transcription and infection
Reversal of Epigenetic Silencing by the SMC5/6 Complex Rescues Integrase-Deficient HIV-1 Replication and Prevents the Establishment of a Latent Reservoir.
No full textIntegration of HIV-1 DNA is an essential step in the viral life cycle, and how the unintegrated proviral DNA intermediate is transcriptionally silenced has been an ongoing question in the field. Here we show that this transcriptional silencing is epigenetic and demonstrate that the Tax transcription factor encoded by Human T-cell Leukemia Virus 1 (HTLV-1) can reverse the repressive epigenetic modifications on unintegrated, episomal HIV-1 circular DNA. Tax expression in HIV-1 mutants lacking functional integrase, and are normally transcriptionally silenced, causes the recruitment of NF-κB to unintegrated viral DNA promoter, reverses the repressive epigenetic modifications on the chromatinzed viral DNA, and leads to a robust, spreading infection. In addition, using an unbiased screen, we identify the host SMC5/6 complex as essential for epigenetically silencing unintegrated/ pre-integrated HIV-1 DNA. The SMC5/6 complex binds chromatinized HIV-1 DNA and triggers epigenetic silencing by inducing its SUMOylation through NSMCE2, an E3 SUMO ligase. Inhibiting this SUMOylation, by knocking out members of the SMC5/6 complex, mutationally disrupting its E3 ligase function, or by using a SUMOylation inhibitors like TAK-981 prevents this epigenetic silencing and rescues both viral gene transcription from, and replication of, integrase-deficient HIV-1. Finally, we show that inhibiting this initial SUMO-mediated silencing of HIV-1 DNA in integration-competent viruses with a functional integrase by the SMC5/6 complex drastically interferes with the establishment of latent HIV-1 infections in both CD4+ T cell lines and primary human T cells. We thus propose a new model to explain the establishment of the HIV-1 latent reservoir.</p
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