The nucleocapsid protein (N) of the severe acute respiratory syndrome coronavirus (SARS-CoV) packages the viral genomic RNA and is crucial for viability. However, the RNA-binding mechanism is poorly understood. We have shown previously that the N protein contains two structural domains-the N-terminal domain (NTD; residues 45 to 181) and the C-terminal dimerization domain (CTD; residues 248 to 365)-flanked by long stretches of disordered regions accounting for almost half of the entire sequence. Small-angle X-ray scattering data show that the protein is in an extended conformation and that the two structural domains of the SARS-CoV N protein are far apart. Both the NTD and the CTD have been shown to bind RNA. Here we show that all disordered regions are also capable of binding to RNA. Constructs containing multiple RNA-binding regions showed Hill coefficients greater than 1, suggesting that the N protein binds to RNA cooperatively. The effect can be explained by the "coupled-allostery" model, devised to explain the allosteric effect in a multidomain regulatory system. Although the N proteins of different coronaviruses share very low sequence homology, the physicochemical features described above may be conserved across different groups of Coronaviridae. The current results underscore the important roles of multisite nucleic acid binding and intrinsic disorder in N protein function and RNP packaging.Severe acute respiratory syndrome (SARS) is the first pandemic of the 21st century that spread to multiple nations, with a fatality rate of ca. 8%. The disease is caused by a novel SARS-associated coronavirus (SARS-CoV) closely related to the group II coronaviruses, which include the human coronavirus OC43 and murine hepatitis virus (6, 18). Traditional antiviral treatments have had little success against SARS during the outbreak, and vaccines have yet to be developed (35).Coronaviruses are positive-sense single-stranded RNA (ssRNA) viruses. The coronavirus genomic RNA is encapsidated into a helical capsid by the nucleocapsid (N) protein, which is one of the most abundant coronavirus proteins (19). The N protein has nonspecific binding activity toward nucleic acids, including ssRNA, single-stranded DNA, and double-stranded DNA (33). It can also act as an RNA chaperone (39). However, the mechanism of binding of the N protein to nucleic acids is poorly understood.The SARS-CoV N protein is a homodimer composed of 422 amino acids (aa) in each chain. The N protein can be divided into two structural domains interspersed with disordered (unstructured) regions (Fig. 1A) (2). The N-terminal domain (NTD; also called RBD) serves as a putative RNA-binding domain, while the C-terminal domain (CTD; also called DD) is a dimerization domain (13,36). Both the NTD and the CTD bind to nucleic acids through electropositive regions on their surfaces (3, 13, 32). All coronaviruses share similar domain architectures at both the sequence and structure levels. No structure of N protein or any of its domains in complex with nucleic acids is ava...

The efficacy of cancer drugs is often limited because only a small fraction of the administered dose accumulates in tumors. Here we report an injectable nanoparticle generator (iNPG) that overcomes multiple biological barriers to cancer drug delivery. The iNPG is a discoidal micrometer-sized particle that can be loaded with chemotherapeutics. We conjugate doxorubicin to poly(L-glutamic acid) via a pH-sensitive cleavable linker, and load the polymeric drug (pDox) into iNPG to assemble iNPG-pDox. Once released from iNPG, pDox spontaneously forms nanometer-sized particles in aqueous solution. Intravenously injected iNPG-pDox accumulates at tumors due to natural tropism and enhanced vascular dynamics and releases pDox nanoparticles that are internalized by tumor cells. Intracellularly, pDox nanoparticles are transported to the perinuclear region and cleaved into Dox, thereby avoiding excretion by drug efflux pumps. Compared to its individual components or current therapeutic formulations, iNPG-pDox shows enhanced efficacy in MDA-MB-231 and 4T1 mouse models of metastatic breast cancer, including functional cures in 40–50% of treated mice.

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The viral spike (S) coat protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) engages the human angiotensin-converting enzyme2 (ACE2) cell surface receptor to infect the host cells. Thus, concerns arose regarding theoretically higher risk for Coronavirus -19 (COVID-19) in patients taking angiotensin-converting enzyme inhibitors (ACEI)/ angiotensin II type 1 receptor antagonists (ARBs). We systematically assessed case-population and cohort studies from MEDLINE (Ovid), Cochrane Database of Systematic Reviews PubMed, Embase, medRXIV, the World Health Organization data-base of COVID-19 publications and ClinicalTrials.gov through Jun 1, 2020, with planned ongoing surveillance. We rated the certainty of evidence according to Cochrane methods and the GRADE approach. After pooling the adjusted odds ratios (aOR) from the included studies, no significant increase was noted in the risk of SARS-CoV-2 infection by the use of ACEi (aOR, 0.95; 95% CI, 0.86-1.05) or ARBs (aOR, 1.05; 95% CI, 0.97-1.14). However, the random-effects meta-regression revealed that age may modify the SARS-CoV-2 infection risk in subjects with the use of ARBs (coefficient, -0.006; 95% CI, -0.016 to 0.004)-i.e.: the use of ARBs, as opposed to ACEi, specifically augmented the risk of SARS-CoV-2 infection in younger subjects (< 60 years-old). The use of ACEi might not increase the susceptibility of SARS-CoV-2 infection, severity of disease and mortality in case-population and cohort studies. Additionally, we found for the first time that the use of ARBs, as opposed to ACEi, specifically augmented the risk of SARS-CoV-2 infection in younger subjects; without obvious effects on COVID-19 outcomes.