Structure and function in the herpes simplex virus 1 RNA-binding protein U(S)11: Mapping of the domain required for ribosomal and nucleolar association and RNA binding in vitro

The herpes simplex virus 1 U(S)11 protein is an RNA-binding regulatory protein that specifically and stably associates vith 60S ribosomal subunits and nucleoli and is incorporated into virions, We report that U(S)11/beta-galactosidase fusion protein expressed in bacteria bound to rRNA from the 60S subunit and not the 30S subunit, This binding reflects the specificity of ribosomal subunit association, Analyses of deletion mutants of the U(S)11 gene showed that specific RNA binding activity, nucleolar localization, and association with 60S ribosomal subunits were found to map to the amino acid sequences of the carboxyl terminus of U(S)11 protein, suggesting that these activities all reflect specific binding of U(S)11 to large subunit rRNA. The carboxyl-terminal half of the protein consists of a regular tripeptide repeat of the sequence RXP and constitutes a completely novel RNA-binding domain. All of the mutant U(S)11 proteins could be incorporated into virus particles, suggesting that the signal for virion incorporation either is at the amino-terminal four amino acids or is redundant in the protein.