So similar, yet so different: selective translation of capped and polyadenylated viral mRNAs in the influenza virus infected cell

Influenza virus is included among the Orthomyxoviridae family and it is a major public health problem causing annual mortality worldwide. Viral mRNAs bear short capped oligonucleotide sequences at their 5'-ends, acquired from host cell pre-mRNAs during viral transcription, and are polyadenylated at their 3'-end. Therefore, viral and cellular mRNAs are undistinguishable from a structural point of view. However, selective translation of viral proteins occurs upon infection, while initiation and elongation steps of cellular mRNA translation are efficiently inhibited. Viruses do not possess the complex machinery required to translate their mRNAs and are then obliged to compete for host-cell factors and manipulate the translation apparatus to their own benefit. Thus, the understanding of the processes that govern viral translation could facilitate the finding of possible targets for anti viral interventions. In the present review, we will point out the mechanisms by which influenza virus takes control of the host-cell protein synthesis machinery to ensure the production of new viral particles. First, we will discuss the mechanisms by which the virus counteracts the anti viral translation repression induced in the infected cell. Next, we will focus on the shut-off of cellular protein synthesis and the specific requirements for the eIF4F complex on influenza mRNA translation. Finally, we will discuss the role of different cellular and viral proteins in the selective translation of viral messengers in the infected cell and we will summarize the proposed mechanisms for the recruitment of cellular translational machinery to the viral mRNAs.