Re-localization of Cellular Protein SRp20 during Poliovirus Infection: Bridging a Viral IRES to the Host Cell Translation Apparatus

Poliovirus IRES-mediated translation requires the functions of certain canonical as well as non-canonical factors for the recruitment of ribosomes to the viral RNA. The interaction of cellular proteins PCBP2 and SRp20 in extracts from poliovirus-infected cells has been previously described, and these two proteins were shown to function synergistically in viral translation. To further define the mechanism of ribosome recruitment for the initiation of poliovirus IRES-dependent translation, we focused on the role of the interaction between cellular proteins PCBP2 and SRp20. Work described here demonstrates that SRp20 dramatically re-localizes from the nucleus to the cytoplasm of poliovirus-infected neuroblastoma cells during the course of infection. Importantly, SRp20 partially co-localizes with PCBP2 in the cytoplasm of infected cells, corroborating our previous in vitro interaction data. In addition, the data presented implicate the presence of these two proteins in viral translation initiation complexes. We show that in extracts from poliovirus-infected cells, SRp20 is associated with PCBP2 bound to poliovirus RNA, indicating that this interaction occurs on the viral RNA. Finally, we generated a mutated version of SRp20 lacking the RNA recognition motif (SRp20ΔRRM) and found that this protein is localized similar to the full length SRp20, and also partially co-localizes with PCBP2 during poliovirus infection. Expression of this mutated version of SRp20 results in a ∼100 fold decrease in virus yield for poliovirus when compared to expression of wild type SRp20, possibly via a dominant negative effect. Taken together, these results are consistent with a model in which SRp20 interacts with PCBP2 bound to the viral RNA, and this interaction functions to recruit ribosomes to the viral RNA in a direct or indirect manner, with the participation of additional protein-protein or protein-RNA interactions

SARS Coronavirus nsp1 Protein Induces Template-Dependent Endonucleolytic Cleavage of mRNAs: Viral mRNAs Are Resistant to nsp1-Induced RNA Cleavage

SARS coronavirus (SCoV) nonstructural protein (nsp) 1, a potent inhibitor of host gene expression, possesses a unique mode of action: it binds to 40S ribosomes to inactivate their translation functions and induces host mRNA degradation. Our previous study demonstrated that nsp1 induces RNA modification near the 5′-end of a reporter mRNA having a short 5′ untranslated region and RNA cleavage in the encephalomyocarditis virus internal ribosome entry site (IRES) region of a dicistronic RNA template, but not in those IRES elements from hepatitis C or cricket paralysis viruses. By using primarily cell-free, in vitro translation systems, the present study revealed that the nsp1 induced endonucleolytic RNA cleavage mainly near the 5′ untranslated region of capped mRNA templates. Experiments using dicistronic mRNAs carrying different IRESes showed that nsp1 induced endonucleolytic RNA cleavage within the ribosome loading region of type I and type II picornavirus IRES elements, but not that of classical swine fever virus IRES, which is characterized as a hepatitis C virus-like IRES. The nsp1-induced RNA cleavage of template mRNAs exhibited no apparent preference for a specific nucleotide sequence at the RNA cleavage sites. Remarkably, SCoV mRNAs, which have a 5′ cap structure and 3′ poly A tail like those of typical host mRNAs, were not susceptible to nsp1-mediated RNA cleavage and importantly, the presence of the 5′-end leader sequence protected the SCoV mRNAs from nsp1-induced endonucleolytic RNA cleavage. The escape of viral mRNAs from nsp1-induced RNA cleavage may be an important strategy by which the virus circumvents the action of nsp1 leading to the efficient accumulation of viral mRNAs and viral proteins during infection

Floral Product Marketing in Greater Los Angeles

Excerpts from the report: The floral products industry in the greater Los Angeles area was surveyed to determine the nature and direction of changes in floral product marketing in Southern California. Researchers focused on the impact changes might have on the retail and wholesale segments of the industry. They also considered the relocation of the wholesale floral markets on Wall Street, in downtown Los Angeles, to another, more suitable site. These two objectives are related since structural changes within the industry affect decisions regarding relocation. Information presented is based on extensive interviews with floral product producers, wholesalers, retailers, and importers. More than 100 individuals were interviewed. Information gathered from the interviews was used in preparing this report. Additional information was gathered from four surveys, two targeting retail florists in the Los Angeles five-county area, one directed at wholesalers located in the Wall Street markets in downtown Los Angeles, and one targeted to all growers of floral products in California and selected growers in neighboring States

Cointegration and market integration: an application to the Indonesian rice market

This article suggests improvements in the use of regression analysis to measure spatial market integration. The procedure pioneered by Ravallion is still widespread but is valid only under certain conditions of exogeneity. The alternative offered here is an error‐correction mechanism which makes it possible to test for exogeneity as well as indicating the direction and strength of causality in price formation between markets. The method is illustrated with data on rice prices in different parts of the Indonesian market. The results confirm, among other things, that supply sources are more important than demand sources in driving prices

Spatial price dynamics and integration in russian food markets

This paper evaluates dynamic elements of spatial market linkages for several important food commodities in the Russian Federation. We argue that delivery lags and other impediments to regional commodity trade may delay price responses. Standard regression and cointegration tests that compare contemporaneous price linkages in a short-run setting may not be flexible enough to address integration in such a setting. As an alternative, we complement conventional time-series tests of spatial integration with an analysis of dynamic responses to price shocks. The results provide tempered support for spatial integration, especially in retail markets. However, the results suggest that, because of gradual adjustments to price shocks, integration may occur mainly in the long run.Cointegration, Market integration, Price dynamics, Transition economies,