A combination of T4 polynucleotide kinase, Escherichia coli alkaline 
phosphatase, yeast Saccharomyces cerevisiae capping enzyme consisting of alpha 
(RNA guanylyltransferase) and beta (RNA 5'-triphosphatase) subunits. and its 
alpha subunit without RNA 5'-phosphatase activity was used to establish a simple 
enzymatic method for determination of RNA species with 5'-hydroxyl, 
5'-monophosphate, 5'-diphosphate or 5'-triphosphate termini. Using this method, 
we found that viral genome RNA (vRNA) segments of both A-type and C-type 
influenza viruses carry tri- or diphosphates at their 5' termini. The conclusion 
was based on the observations that: (i) 5' phosphorylation of vRNAs by T4 
polynucleotide kinase takes place only after phosphatase treatment; and (ii) 
capping of vRNAs can be observed with both the intact yeast capping enzyme and 
its alpha subunit alone devoid of RNA 5'-triphosphatase activity; but (iii) the 
level of capping is higher for the alphabeta holoenzyme than the alpha subunit 
though the relative level varies depending on RNA preparations. The results 
support the de novo initiation for the RNA replication although transcription of 
influenza vRNAs is initiated by host cell capped RNAs as primers.