Extremely efficient cleavage of eIF4G by picornaviral proteinases L and 2Ain vitro

Certain picornaviruses encode proteinases which cleave the translation init iation factor eIF4G, a member of the eIF4F complex which recruits mRNA to t he 40S ribosomal subunit during initiation of protein synthesis in eukaryot es. We have compared the efficiency of eIF4G cleavage in rabbit reticulocyt e lysates during translation of mRNAs encoding the foot-and-mouth disease v irus leader proteinase (L-pro) or the human rhinovirus 2A(pro), Under stand ard translation conditions, L-pro cleaved 50% of eIF4G within 4 min after i nitiation of protein synthesis, whereas 2A(pro) required 15 min. At these t imes, the molar ratios of proteinase to eIF4G were 1:130 for L-pro and 1:12 for 2A(pro), indicating a much more efficient in vitro cleavage than previ ously observed. The molar ratios are similar to those observed during viral infection in vivo. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.