instruction:
In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
question:
Ebola virus (EboV) belongs to the Filoviridae family of viruses that causes severe and fatal hemhorragic fever. Infection by EboV involves fusion between the virus and host cell membranes mediated by the envelope glycoprotein GP2 of the virus. Similar to the envelope glycoproteins of other viruses, the central feature of the GP2 ectodomain postfusion structure is a six-helix bundle formed by the protein's N-and C-heptad repeat regions (NHR and CHR, respectively). Folding of this six-helix bundle provides the energetic driving force for membrane fusion; in other viruses, designed agents that disrupt formation of the six-helix bundle act as potent fusion inhibitors. To interrogate determinants of EboV GP2-mediated membrane fusion, we designed model proteins that consist of the NHR and CHR segments linked by short protein linkers. Circular dichroism and gel filtration studies indicate that these proteins adopt stable ahelical folds consistent with design. Thermal denaturation indicated that the GP2 six-helix bundle is highly stable at pH 5.3 (melting temperature, T m , of 86.8 6 2.0C and van't Hoff enthalpy, DH vH , of 228.2 6 1.0 kcal/mol) and comparable in stability to other viral membrane fusion six-helix bundles. We found that the stability of our designed a-helical bundle proteins was dependent on buffering conditions with increasing stability at lower pH. Small pH differences (5.3-6.1) had dramatic effects (DT m 5 37C) suggesting a mechanism for conformational control that is dependent on environmental pH. These results suggest a role for low pH in stabilizing six-helix bundle formation during the process of GP2-mediated viral membrane fusion.
answer:
Designed protein mimics of the Ebola virus glycoprotein GP2 a-helical bundle: Stability and pH effects

question:
Chronic infection and cancer are associated with suppressed T cell responses in the presence of cognate antigen. Recent work identified memory-like CXCR5 + TCF1 + CD8 + T cells that sustain T cell responses during persistent infection and proliferate upon anti-PD1 treatment. Approaches to expand these cells are sought. We show that blockade of interferon type 1 (IFN-I) receptor leads to CXCR5 + CD8 + T cell expansion in an IL-27-and STAT1-dependent manner. IFNAR1 blockade promoted accelerated cell division and retention of TCF1 in virus-specific CD8 + T cells. We found that CD8 + T cell-intrinsic IL-27 signaling safeguards the ability of TCF1 hi cells to maintain proliferation and avoid terminal differentiation or programmed cell death. Mechanistically, IL-27 endowed rapidly dividing cells with IRF1, a transcription factor that was required for sustained division in a cell-intrinsic manner. These findings reveal that IL-27 opposes IFN-I to uncouple effector differentiation from cell division and suggest that IL-27 signaling could be exploited to augment self-renewing T cells in chronic infections and cancer.
answer:
IL-27 promotes the expansion of self-renewing CD8 + T cells in persistent viral infection

question:
We have solved the three-dimensional crystal structure of the stem-loop II motif (s2m) RNA element of the SARS virus genome to 2.7-A resolution. SARS and related coronaviruses and astroviruses all possess a motif at the 39 end of their RNA genomes, called the s2m, whose pathogenic importance is inferred from its rigorous sequence conservation in an otherwise rapidly mutable RNA genome. We find that this extreme conservation is clearly explained by the requirement to form a highly structured RNA whose unique tertiary structure includes a sharp 908 kink of the helix axis and several novel longer-range tertiary interactions. The tertiary base interactions create a tunnel that runs perpendicular to the main helical axis whose interior is negatively charged and binds two magnesium ions. These unusual features likely form interaction surfaces with conserved host cell components or other reactive sites required for virus function. Based on its conservation in viral pathogen genomes and its absence in the human genome, we suggest that these unusual structural features in the s2m RNA element are attractive targets for the design of anti-viral therapeutic agents. Structural genomics has sought to deduce protein function based on three-dimensional homology. Here we have extended this approach to RNA by proposing potential functions for a rigorously conserved set of RNA tertiary structural interactions that occur within the SARS RNA genome itself. Based on tertiary structural comparisons, we propose the s2m RNA binds one or more proteins possessing an oligomer-binding-like fold, and we suggest a possible mechanism for SARS viral RNA hijacking of host protein synthesis, both based upon observed s2m RNA macromolecular mimicry of a relevant ribosomal RNA fold. Citation: Robertson MP, Igel H, Baertsch R, Haussler D, Ares M, et al. (2004) The structure of a rigorously conserved RNA element within the SARS virus genome. PLoS Biol 3(1): e5. PLoS Biology | www.plosbiology.org January 2005 | Volume 3 | Issue 1 | e5 0086 Open access, freely available online PL o S BIOLOGY PLoS Biology | www.plosbiology.org January 2005 | Volume 3 | Issue 1 | e5 0087 Crystal Structure of SARS s2m RNA PLoS Biology | www.plosbiology.org
answer:
The Structure of a Rigorously Conserved RNA Element within the SARS Virus Genome