In vivo aminoacylation of brome mosaic and barley stripe mosaic virus RNAs

Abstract

The genomic RNAs of several plant viruses are now known to be able to bind a specific amino acid at their 3′ ends in a tRNA-like manner. Where the nucleotide sequence of the 3′-terminal region is known, it can be folded into an extensively base-paired secondary structure having the essential features of tRNAs1,2. The high degree of nucleotide sequence conservation of the 3′-terminal regions of the four RNAs of the three known bromoviruses3, and the loss of infectivity of brome mosaic virus (BMV) RNA after chemical modification of its 3′ end4, strongly suggest that the tRNA-like structure has a biological function in infection2. To elucidate this it has been important to determine whether viral RNAs are aminoacylated within infected host cells. We studied BMV and barley stripe mosaic virus (BSMV), which belong to very different groups but which have genomic RNAs that are capable of both accepting tyrosine and infecting barley protoplasts. We report here that single-stranded RNAs of both viruses are aminoacylated in vivo, but that the encapsidated RNAs of BMV are not.