Owing to the step-wise release of polymerases from each gene junction, our simulations estimated the gradual decrease of VSV mRNA synthesis in the order of N . P . M . G . L ( Figure 1A ). Compared with the most abundant N mRNA, L mRNA is very scanty in infected baby hamster kidney (BHK) cells (40 ; 140-fold less). The relative production level of each protein matched the relative availability of the corresponding mRNAs ( Figure 1B ) even though different proteins degrade at different rates ( Table 1 ). Because of the different level of incorporation of each protein into a single virion particle, as defined by the protein stoichiometry (Table 2 , [28, 29] ), the relative levels of free viral proteins in the cytoplasm develop differently from their mRNA levels ( Figure 1C ). P protein is most abundant owing to its low content in the virion, and L and N proteins are least abundant. The persistently low level of N protein is related to its immediate complexation with nascent genomes and antigenomes to make nucleocapsid particles during the replication step. Owing to the cyclic switching between transcription and replication by the encapsidation process, the N protein level is predicted to oscillate as shown in Figure 1C .