Molecular insights into the function of the viral RNA silencing suppressor HCPro

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Ivanov , K , Eskelin , K J , Bašić , M , Swarnalok , D , Lohmus , A , Varjosalo , M T & Mäkinen , K M 2016 , ' Molecular insights into the function of the viral RNA silencing suppressor HCPro ' , Plant Journal , vol. 85 , no. 1 , pp. 30-45 . https://doi.org/10.1111/tpj.13088

Title: Molecular insights into the function of the viral RNA silencing suppressor HCPro
Author: Ivanov, Konstantin; Eskelin, Katri Johanna; Bašić, Marta; Swarnalok, De; Lohmus, Andres; Varjosalo, Markku Tapio; Mäkinen, Kristiina Maria
Contributor: University of Helsinki, Department of Food and Nutrition
University of Helsinki, Biosciences
University of Helsinki, Plant-Virus Interactions
University of Helsinki, Department of Food and Nutrition
University of Helsinki, Institute of Biotechnology
University of Helsinki, Department of Food and Nutrition
Date: 2016
Language: eng
Number of pages: 16
Belongs to series: Plant Journal
ISSN: 0960-7412
URI: http://hdl.handle.net/10138/297740
Abstract: Potyviral helper component proteinase (HCPro) is a well-characterized suppressor of antiviral RNA silencing, but its mechanism of action is not yet fully understood. In this study, we used affinity purification coupled with mass spectrometry to identify binding partners of HCPro in potyvirus-infected plant cells. This approach led to identification of various HCPro interactors, including two key enzymes of the methionine cycle, S–adenosyl-l–methionine synthase and S–adenosyl-l–homocysteine hydrolase. This finding, together with the results of enzymatic activity and gene knockdown experiments, suggests a mechanism in which HCPro complexes containing viral and host proteins act to suppress antiviral RNA silencing through local disruption of the methionine cycle. Another group of HCPro interactors identified in this study comprised ribosomal proteins. Immunoaffinity purification of ribosomes demonstrated that HCPro is associated with ribosomes in virus-infected cells. Furthermore, we show that HCPro and ARGONAUTE1 (AGO1), the core component of the RNA-induced silencing complex (RISC), interact with each other and are both associated with ribosomes in planta. These results, together with the fact that AGO1 association with ribosomes is a hallmark of RISC-mediated translational repression, suggest a second mechanism of HCPro action, whereby ribosome-associated multiprotein complexes containing HCPro relieve viral RNA translational repression through interaction with AGO1.
Subject: 1183 Plant biology, microbiology, virology
Potyvirus, HCPro, RNA silencing, silencing supressor, Nicotiana benthamiana, methionin cycle, translational repression, Argonaute, SAM, SAMS, SAHH
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