Howard Hughes Medical Institute

About: Howard Hughes Medical Institute is a nonprofit organization based out in Chevy Chase, Maryland, United States. It is known for research contribution in the topics: Gene & RNA. The organization has 20371 authors who have published 34677 publications receiving 5247143 citations. The organization is also known as: HHMI & hhmi.org.

Convergent antibody responses to SARS-CoV-2 in convalescent individuals.

Abstract: During the COVID-19 pandemic, SARS-CoV-2 infected millions of people and claimed hundreds of thousands of lives Virus entry into cells depends on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (S) Although there is no vaccine, it is likely that antibodies will be essential for protection However, little is known about the human antibody response to SARS-CoV-21-5 Here we report on 149 COVID-19 convalescent individuals Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal pseudovirus neutralizing titres: less than 1:50 in 33% and below 1:1,000 in 79%, while only 1% showed titres above 1:5,000 Antibody sequencing revealed expanded clones of RBD-specific memory B cells expressing closely related antibodies in different individuals Despite low plasma titres, antibodies to three distinct epitopes on RBD neutralized at half-maximal inhibitory concentrations (IC50 values) as low as single digit nanograms per millitre Thus, most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective

Structures of a histone deacetylase homologue bound to the TSA and SAHA inhibitors.

Abstract: Histone deacetylases (HDACs) mediate changes in nucleosome conformation and are important in the regulation of gene expression HDACs are involved in cell-cycle progression and differentiation, and their deregulation is associated with several cancers HDAC inhibitors, such as trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA), have anti-tumour effects, as they can inhibit cell growth, induce terminal differentiation and prevent the formation of tumours in mice models, and they are effective in the treatment of promyelocytic leukemia Here we describe the structure of the histone deacetylase catalytic core, as revealed by the crystal structure of a homologue from the hyperthermophilic bacterium Aquifex aeolicus, that shares 352% identity with human HDAC1 over 375 residues, deacetylates histones in vitro and is inhibited by TSA and SAHA The deacetylase, deacetylase-TSA and deacetylase-SAHA structures reveal an active site consisting of a tubular pocket, a zinc-binding site and two Asp-His charge-relay systems, and establish the mechanism of HDAC inhibition The residues that make up the active site and contact the inhibitors are conserved across the HDAC family These structures also suggest a mechanism for the deacetylation reaction and provide a framework for the further development of HDAC inhibitors as antitumour agents

Atomic structure of the ectodomain from HIV-1 gp41

Abstract: Fusion of viral and cellular membranes by the envelope glycoprotein gp120/gp41 effects entry of HIV-1 into the cell. The precursor, gp160, is cleaved post-translationally into gp120 and gp41 which remain non-covalently associated. Binding to both CD4 and a co-receptor leads to the conformational changes in gp120/gp41 needed for membrane fusion. We used X-ray crystallography to determine the structure of the protease-resistant part of a gp41 ectodomain solubilized with a trimeric GCN4 coiled coil in place of the amino-terminal fusion peptide. The core of the molecule is found to be an extended, triple-stranded alpha-helical coiled coil with the amino terminus at its tip. A carboxy-terminal alpha-helix packs in the reverse direction against the outside of the coiled coil, placing the amino and carboxy termini near each other at one end of the long rod. These features, and the existence of a similar reversal of chain direction in the fusion pH-induced conformation of influenza virus HA2 and in the transmembrane subunit of Moloney murine leukaemia virus (Fig. 1a-d), suggest a common mechanism for initiating fusion.

Dasatinib in Imatinib-Resistant Philadelphia Chromosome–Positive Leukemias

Abstract: Background The BCR-ABL tyrosine kinase inhibitor imatinib is effective in Philadelphia chromosome–positive (Ph-positive) leukemias, but relapse occurs, mainly as a result of the outgrowth of leukemic subclones with imatinib-resistant BCR-ABL mutations. We evaluated dasatinib, a BCR-ABL inhibitor that targets most imatinib-resistant BCRABL mutations, in patients with chronic myelogenous leukemia (CML) or Ph-positive acute lymphoblastic leukemia (ALL). Methods Patients with various phases of CML or with Ph-positive ALL who could not tolerate or were resistant to imatinib were enrolled in a phase 1 dose-escalation study. Dasatinib (15 to 240 mg per day) was administered orally in four-week treatment cycles, once or twice daily. Results A complete hematologic response was achieved in 37 of 40 patients with chronicphase CML, and major hematologic responses were seen in 31 of 44 patients with accelerated-phase CML, CML with blast crisis, or Ph-positive ALL. In these two phases, the rates of major cytogenetic response were 45 percent and 25 percent, respectively. Responses were maintained in 95 percent of patients with chronic-phase disease and in 82 percent of patients with accelerated-phase disease, with a median follow-up more than 12 months and 5 months, respectively. Nearly all patients with lymphoid blast crisis and Ph-positive ALL had a relapse within six months. Responses occurred among all BCR-ABL genotypes, with the exception of the T315I mutation, which confers resistance to both dasatinib and imatinib in vitro. Myelosuppression was common but not dose-limiting. Conclusions Dasatinib induces hematologic and cytogenetic responses in patients with CML or Ph-positive ALL who cannot tolerate or are resistant to imatinib. (ClinicalTrials.gov number, NCT00064233.)

Heart Regeneration in Zebrafish

Abstract: Cardiac injury in mammals and amphibians typically leads to scarring, with minimal regeneration of heart muscle. Here, we demonstrate histologically that zebrafish fully regenerate hearts within 2 months of 20% ventricular resection. Regeneration occurs through robust proliferation of cardiomyocytes localized at the leading epicardial edge of the new myocardium. The hearts of zebrafish with mutations in the Mps1 mitotic checkpoint kinase, a critical cell cycle regulator, failed to regenerate and formed scars. Thus, injury-induced cardiomyocyte proliferation in zebrafish can overcome scar formation, allowing cardiac muscle regeneration. These findings indicate that zebrafish will be useful for genetically dissecting the molecular mechanisms of cardiac regeneration.