INTERACTION OF TURNIP YELLOW MOSAIC-VIRUS VAL-RNA WITH EUKARYOTIC ELONGATION-FACTOR EF-1-ALPHA - SEARCH FOR A FUNCTION

The 3''-terminal tRNA-like structure in turnip yellow mosaic virus (TYMV) RNA can be adenylated by tRNA nucleotidyltransferase and subsequently aminoacylated by valyl-tRNA synthetase. Here we present evidence that TYMV Val-RNA can form a stable complex with eukaryotic wheat germ elongation factor EF-1.alpha. and GTP: theVal-RNA is protected by EF-1.alpha. .cntdot. GTP against digestion by RNase A. By affinity chromatography of TYMV Val-RNA fragments on immobilized EF-1.alpha. .cntdot. GTP, it has been established that the valylated aminoacyl RNA domain, which in TYMV RNA is formed by the 3'' half of the tRNA-like region, is sufficient for complex formation with EF-1.alpha. .cntdot. GTP. The aminoacyl RNA domain is equivalent in tRNAs to the continuous helix formed by the acceptor stem and the T stem and loop. In line with these results, the aminoacyl RNA domain in TYMV Val-RNA complexed to EF-1.alpha. .cntdot. GTP is resistant to digestion by RNase A. It is also shown that the TYMV RNA replicase (RNA-dependent RNA polymerase) isolated from TYMV-infected Chinese cabbage leaves does not contain tRNA nucleotidyltransferase, valyl-tRNA synthetase or EF-1.alpha.. This suggests that interaction of TYMV RNA with EF-1.alpha. is not mandatory for replicase activity.