Samji: Influenza A: understanding the viral life cycle 157 proteins and glycolipids. removes these sialic acids. Without this process, the viral particle would not be released from the plasma membrane [60]. CONCLUSION This is just a brief overview of the steps in the influenza A viral life cycle from entry into a host cell to exit from the host cell. This is a very complicated process, and there is much still to be learned, such as the com- plete mechanism of viral genomic RNA replication. Like all viruses, influenza A has evolved to take advantage of host cells by processes such as “cap-snatching” and inhi- bition of cellular mRNA splicing and export. Influenza A can be a deadly virus causing many pandemics. We hope that by learning how the virus is able to replicate in host cells, we can develop better drugs and vac- cines to protect us. REFERENCES 1. Fields BN, Knipe DM, Howley PM. Fields virology. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2007. 2. Scheiffele P, Rietveld A, Wilk T, Simons K. Influenza viruses select ordered lipid do- mains during budding from the plasma mem- brane. J Biol Chem. 1999;274(4):2038-44. 3. Zhang J, Pekosz A, Lamb RA. Influenza virus assembly and lipid raft microdomains: a role for the cytoplasmic tails of the spike glycoproteins. J Virol. 2000;74(10):4634-44. 4. Nayak DP, Balogun RA, Yamada H, Zhou ZH, Barman S. Influenza virus morphogene- sis and budding. Virus Res. 2009;143(2):147- 61. 5. Schroeder C, Heider H, Moncke-Buchner E, Lin TI. The influenza virus ion channel and maturation cofactor M2 is a cholesterol-bind- ing protein. Eur Biophys J. 2005;34(1):52-66. 6. Nayak DP, Hui EK, Barman S. Assembly and budding of influenza virus. Virus Res. 2004;106(2):147-65. 7. Skehel JJ, Wiley DC. Receptor binding and membrane fusion in virus entry: the influenza hemagglutinin. Annu Rev Biochem. 2000;69:531-69. 8. Huang Q, Sivaramakrishna RP, Ludwig K, Korte T, Bottcher C, Herrmann A. Early steps of the conformational change of influenza virus hemagglutinin to a fusion active state: stability and energetics of the hemagglutinin. Biochim Biophys Acta. 2003;1614(1):3-13. 9. Holsinger LJ, Lamb RA. Influenza virus M2 integral membrane protein is a homotetramer stabilized by formation of disulfide bonds. Virology.1991;183(1):32-43. 10. Pinto LH, Holsinger LJ, Lamb RA. Influenza virus M2 protein has ion channel activity. Cell. 1992;69(3):517-28. 11. Pinto LH, Lamb RA. The M2 proton chan- nels of influenza A and B viruses. J Biol Chem. 2006;281(14):8997-9000. 12. Boulo S, Akarsu H, Ruigrok RW, Baudin F. Nuclear traffic of influenza virus proteins and ribonucleoprotein complexes. Virus Res. 2007;124(1-2):12-21. 13. Crow M, Deng T, Addley M, Brownlee GG. Mutational analysis of the influenza virus cRNA promoter and identification of nu- cleotides critical for replication. J Virol. 2004;78(12):6263-70. 14. Deng T, Vreede FT, Brownlee GG. Different de novo initiation strategies are used by in- fluenza virus RNA polymerase on its cRNA and viral RNA promoters during viral RNA replication. J Virol. 2006;80(5):2337-48. 15. Flick R, Neumann G, Hoffmann E, Neumeier E, Hobom G. Promoter elements in the in- fluenza vRNA terminal structure. RNA. 1996;2(10):1046-57. 16. Azzeh M, Flick R, Hobom G. Functional analy- sis of the influenza A virus cRNA promoter and construction of an ambisense transcription sys- tem. Virology. 2001;289(2):400-10. 17. Plotch SJ, Tomasz J, Krug RM. Absence of detectable capping and methylating enzymes in influenza virions. J Virol. 1978;28(1):75- 83. 18. Krug RM, Morgan MA, Shatkin AJ. Influenza viral mRNA contains internal N6-methy- ladenosine and 5'-terminal 7-methylguanosine in cap structures. J Virol. 1976;20(1):45-53. 19. Dhar R, Chanock RM, Lai CJ. Nonviral oligonucleotides at the 5' terminus of cyto- plasmic influenza viral mRNA deduced from cloned complete genomic sequences. Cell. 1980;21(2):495-500. 20. Bouloy M, Plotch SJ, Krug RM. Globin mRNAs are primers for the transcription of influenza viral RNA in vitro. Proc Natl Acad Sci USA. 1978;75(10):4886-90. 21. Plotch SJ, Bouloy M, Krug RM. Transfer of 5'-terminal cap of globin mRNA to influenza viral complementary RNA during transcrip- tion in vitro. Proc Natl Acad Sci USA. 1979;76(4):1618-22. 22. Plotch SJ, Bouloy M, Ulmanen I, Krug RM. A unique cap(m7GpppXm)-dependent influenza virion endonuclease cleaves capped RNAs to generate the primers that initiate viral RNA transcription. Cell.1981;23(3):847-58. 23. Bouloy M, Morgan MA, Shatkin AJ, Krug RM. Cap and internal nucleotides of reovirus mRNA primers are incorporated into in- fluenza viral complementary RNA during transcription in vitro. J Virol. 1979;32(3):895- 904. 24. Bouloy M, Plotch SJ, Krug RM. Both the 7- methyl and the 2'-O-methyl groups in the cap