Apical Transport of Influenza A Virus Ribonucleoprotein Requires Rab11-positive Recycling Endosome

Influenza A virus RNA genome exists as eight-segmented ribonucleoprotein complexes containing viral RNA polymerase and nucleoprotein (vRNPs). Packaging of vRNPs and virus budding take place at the apical plasma membrane (APM). However, little is known about the molecular mechanisms of apical transport of newly synthesized vRNP. Transfection of fluorescent-labeled antibody and subsequent live cell imaging revealed that punctate vRNP signals moved along microtubules rapidly but intermittently in both directions, suggestive of vesicle trafficking. Using a series of Rab family protein, we demonstrated that progeny vRNP localized to recycling endosome (RE) in an active/GTP-bound Rab11-dependent manner. The vRNP interacted with Rab11 through viral RNA polymerase. The localization of vRNP to RE and subsequent accumulation to the APM were impaired by overexpression of Rab binding domains (RBD) of Rab11 family interacting proteins (Rab11-FIPs). Similarly, no APM accumulation was observed by overexpression of class II Rab11-FIP mutants lacking RBD. These results suggest that the progeny vRNP makes use of Rab11-dependent RE machinery for APM trafficking

Structural insight into cap-snatching and RNA synthesis by influenza polymerase.

International audienceInfluenza virus polymerase uses a capped primer, derived by 'cap-snatching' from host pre-messenger RNA, to transcribe its RNA genome into mRNA and a stuttering mechanism to generate the poly(A) tail. By contrast, genome replication is unprimed and generates exact full-length copies of the template. Here we use crystal structures of bat influenza A and human influenza B polymerases (FluA and FluB), bound to the viral RNA promoter, to give mechanistic insight into these distinct processes. In the FluA structure, a loop analogous to the priming loop of flavivirus polymerases suggests that influenza could initiate unprimed template replication by a similar mechanism. Comparing the FluA and FluB structures suggests that cap-snatching involves in situ rotation of the PB2 cap-binding domain to direct the capped primer first towards the endonuclease and then into the polymerase active site. The polymerase probably undergoes considerable conformational changes to convert the observed pre-initiation state into the active initiation and elongation states

Microbial metabolites as biological control agents in food safety

Ensuring food safety and at the same time meeting such demands for retention of nutrition and quality attributes have resulted in increased interest in alternative preservation techniques for inactivating microorganisms and enzymes in foods. This increasing demand has opened new dimensions for the use of natural preservatives derived from plants, animals, or microflora. Extensive research has investigated the potential application of natural antimicrobial agents in food preservation. Especially the significance and use of microbes as producers of antimicrobial metabolites has increased significantly during the last decades. Reported studies have demonstrated that microbial metabolites from microorganisms exhibited a great numbers of diverse and versatile biological effects about antimicrobial activities. These microorganisms produce many compounds that are active against other microorganisms, which can be harnessed to inhibit the growth of potential spoilage or pathogenic microorganisms. These include fermentation end products (metabolites) such as organic acids, hydrogen peroxide, and diacetyl, biofilm, exopolysaccharides in addition to bacteriocins and other antagonistic compounds such as reuterin. Up to now, antimicrobial metabolites from lactic acid bacteria (such as nisin) have been mostly used in food preservation. In addition to lactic acid bacteria, some yeast, mold, and another bacteria species as well as some pathogenic bacteria can produce antimicrobial metabolites. Antimicrobial metabolites present in foods can extend the shelf life of unprocessed or processed foods by reducing the microbial growth rate or viability. This offers a new knowledge-based approach to the exploitation of bacteria for food production, from metabolic engineering of microorganisms to produce antimicrobials or nutritionals, to the molecular mining of activities as yet unknown but which could benefit food production. In addition, the availability of the genomes of many food pathogenic and spoilage bacteria may open up new possibilities for the design of novel antimicrobials which target essential functions of these problematic bacteria. In this chapter, antimicrobial metabolites from microorganism in food safety as a biocontrol agent reviewed. © 2014, Springer Science+Business Media New York