TAILIEUCHUNG - Báo cáo khoa học: The potyviral virus genome-linked protein VPg forms a ternary complex with the eukaryotic initiation factors eIF4E and eIF4G and reduces eIF4E affinity for a mRNA cap analogue

The virus protein linked to the genome (VPg) of plant potyviruses is a 25-kDa protein covalently attached to the genomic RNA 5¢ end. It was previously reported that VPg binds specifically to eIF4E, the mRNAcap-binding protein of the eukaryotic translation initiation complex. We per-formed a spectroscopic study of the interactions between lettuce eIF4E and VPg from lettuce mosaic virus (LMV). | iFEBS Journal The potyviral virus genome-linked protein VPg forms a ternary complex with the eukaryotic initiation factors eIF4E and eIF4G and reduces eIF4E affinity for a mRNA cap analogue Thierry Michon Yannick Estevez Jocelyne Walter Sylvie German-Retana and Olivier Le Gall Interactions Plante-Virus UMR GDPP INRA-Bordeaux 2 Institut de Biologie Vegetale Moleculaire Villenave d Ornon France Keywords eIF4E eIF4G fluorescence interaction VPg Correspondence T. Michon Virologie Vegetale GDPP IBVM-INRA BP 81 33883 Villenave d Ornon Cedex France Fax 33 5 57 12 23 84 Tel 33 5 57 12 23 91 E-mail michon@ Website http ipv Received 10 October 2005 revised 23 January 2006 accepted 26 January 2006 doi The virus protein linked to the genome VPg of plant potyviruses is a 25-kDa protein covalently attached to the genomic RNA 5 end. It was previously reported that VPg binds specifically to eIF4E the mRNAcap-binding protein of the eukaryotic translation initiation complex. We performed a spectroscopic study of the interactions between lettuce eIF4E and VPg from lettuce mosaic virus LMV . The cap analogue m7GDP and VPg bind to eIF4E at two distinct sites with similar affinity Kd pM . A deeper examination of the interaction pathway showed that the binding of one ligand induces a decrease in the affinity for the other by a factor of 15. GST pull-down experiments from plant extracts revealed that VPg can specifically trap eIF4G the central component of the complex required for the initiation of protein translation. Our data suggest that eIF4G recruitment by VPg is indirectly mediated through VPg-eIF4E association. The strength of interaction between eIF4E and pep4G the eIF4E-binding domain on eIF4G was increased significantly by VPg. Taken together these quantitative data show that VPg is an efficient modulator of eIF4E biochemical functions. Lettuce mosaic virus LMV is a member of the genus Potyvirus 1 . .

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