**6. Conclusion**

This chapter explored the viral diversity of enzymatic activities and mechanistic pathways converging to the maturation of the 5' cap on viral RNA. The cap structure provides tremen‐ dous advantages to eukaryotic viruses in terms of vRNA stability, gene translation and immune evasion. Some viruses have evolved enzymatic mechanisms of action unknown to the eukaryotic domain in order to synthesize this critical structure. Other viruses have developed novel cap synthesis mechanisms that generate a 5' cap structure chemically identical to their hosts, yet formed by an entirely new process. Finally, particular viruses have also evolved unique mechanisms to steal or mimic the host cap structure. In conclusion, the incredible diversity and conservation of the mechanisms evolved by viruses to synthesize, acquire or mimic the 5' cap structure is a testimony to the importance of viral RNA capping for viral replication, fitness and infectivity.
