Cross-Urban Point-of-Interest Recommendation for Non-Natives

This article describes how understanding human mobility behavior is of great significance for predicting a broad range of socioeconomic phenomena in contemporary society. Although many studies have been conducted to uncover behavioral patterns of intra-urban and inter-urban human mobility, a fundamental question remains unanswered: To what degree is human mobility behavior predictable in new cities—a person has never visited before? Location-based social networks with a large volume of check-in records provide an unprecedented opportunity to investigate cross-urban human mobility. The authors' empirical study on millions of records from Foursquare reveals the motives and behavioral patterns of non-natives in 59 cities across the United States. Inspired by the ideology of transfer learning, the authors also propose a machine learning model, which is designed based on the regularities that they found in this study, to predict cross-urban human whereabouts after non-natives move to new cities. The experimental results validate the effectiveness and efficiency of the proposed model, thus allowing us to predict and control activities driven by cross-urban human mobility, such as mobile recommendation, visual (personal) assistant, and epidemic prevention

RNA Synthesis by the Brome Mosaic Virus RNA-Dependent RNA Polymerase: Transition from Initiation to Elongation

AbstractThe initiation and elongation phases of (−)-strand RNA synthesisin vitroby the brome mosaic virus RNA-dependent RNA polymerase (RdRp) are differentially sensitive to inhibitors. In an attempt to characterize further the transition RdRp makes from initiation to elongation, we determined the conditions needed to pause the ternary complex and complete only one round of RNA synthesis. During the transition we were able to discern step-wise increases in the affinity of RdRp for RNA by measuring sensitivity to heparin and competition for RdRp by an alternative template. Three distinct stability levels of RdRp–template interactions were found. The first stable RdRp–RNA complex was observed when RdRp bound to the RNA template. A further increase occurred when RdRp synthesized the first phosphodiester bond. A final increase occurred upon formation of between 3 and 13 phosphodiester bonds. After this last transition, RdRp appeared to be tightly committed to the template RNA. These results are analogous to the mechanism of action of DNA-dependent RNA polymerases and are relevant to protein–RNA interaction and template switching by an RdRp

Subgenomic RNA Promoters Dictate the Mode of Recognition by Bromoviral RNA-Dependent RNA Polymerases

AbstractBoth the brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMV) RNA-dependent RNA polymerases (RdRps) were found to recognize the BMV core subgenomic promoter in the same manner, requiring specific functional groups at positions −17, −14, −13, and −11 relative to the subgenomic initiation site (+1). For CCMV subgenomic RNA synthesis, both RdRps required the same nucleotides and four additional nucleotides at positions −20, −16, −15, and −10. The −20 nucleotide is partially responsible for the differential mode of recognition of the two promoters. These data provide evidence that the RNA can induce RdRps to alter the mode of promoter recognition

Characterization of RNA Products Associated with or Aborted by a Viral RNA-Dependent RNA Polymerase

AbstractTernary RNA-dependent RNA polymerase complexes were arrested at various stages of synthesisin vitroby limiting one or more NTPs. The RNAs synthesized prior to/during the arrest of the complex were characterized and the ability of the arrested complexes to continue elongation of these nascent RNAs in the presence of all four NTPs was analyzed. Nascent RNAs of 10 nt and longer remained associated with the RdRp complex and could be extended into full-length RNAs while shorter nascent RNAs were released by the complex. These results establish that previously observed RdRp-synthesized oligoribonucleotides of 8 nt or less are abortive initiation products and confirms that RdRp undergoes a transition from initiation to elongation after the synthesis of 8 nt

Sequences 5′ of the Conserved tRNA-like Promoter Modulate the Initiation of Minus-Strand Synthesis by the Brome Mosaic Virus RNA-Dependent RNA Polymerase

AbstractEach of the brome mosaic virus (BMV) genomic RNAs contains a conserved tRNA-like structure that is sufficient to direct minus-strand RNA synthesisin vitro.The tRNA-like promoters, tB1 and tB3, direct approximately equal amounts of synthesisin vitro.However, 5′ sequences were found to affect the amount of minus-strand synthesis, suggesting that sequences beyond the tRNA-like structure are important in moderating minus-strand synthesis. Consistent with this, sequences upstream the tRNA-like structure are able to partially suppress mutations at or near the initiation site. This activity is observed in the 5′ sequences of both BMV and CMV (cucumber mosaic virus) templates. However, a chimeric RNA containing the CMV tRNA-like promoter fused to the 5′ sequences of BMV was not able to suppress mutations at the initiation site, suggesting that homologous 5′ and 3′ sequences are required to affect initiation. The ability to suppress mutations at the initiation site was correlated with a slight increase in the ability of the BMV RNA-dependent RNA polymerase to interact with the RNA

De Novo Initiation of Viral RNA-Dependent RNA Synthesis

AbstractRNA viruses use several initiation strategies to ensure that their RNAs are synthesized in appropriate amounts, have correct termini, and can be translated efficiently. Many viruses with genomes of single-stranded positive-, negative-, and double-stranded RNA initiate RNA synthesis by a de novo (primer-independent) mechanism. This review summarizes biochemical features and variations of de novo initiation in viral RNA replication

De NovoInitiation of RNA Synthesis by a Recombinant Flaviridae RNA-dependent RNA Polymerase

AbstractRecombinant RNA-dependent RNA polymerases have been reported to synthesize RNAs by extending from the 3′ hydroxyl of a template or an oligonucleotide primer.De novoinitiation has not been reported. Establishment of such an assay would facilitate the analysis of the initiation requirements and allow the testing of antiviral compounds specifically targeting initiation. Using chemically synthesized RNAs and DNAs, we demonstrate that the recombinant RNA-dependent RNA polymerase (NS5B) of bovine viral diarrhea virus initiatesde novoRNA synthesis. Nucleotides required for efficient initiation of RNA synthesis and for stable interaction with NS5B were identified