Printed in Great Britain 449 Quantification of Influenza Virus Messenger RNAs

The amounts of specific influenza virus cRNAs present on polyribosomes ofcells treated with cycloheximide atvarious times after infection were measured by quan-titative hybridization with 12~I-labelled virus RNA segments. All species of cRNA were found associated with polyribosomes at every time point analysed. The relative abundance of the specific RNAs was in the same order as the reported rel-ative "synthesis of the influenza virus proteins. However, the concentrations of the cRNAs spanned a considerably smaller range than published protein synthetic rates, suggesting that both transcriptional nd translational controls operate to regulate the final levels of influenza virus polypeptide synthesis