Short and Sweet: Viral 5`-UTR as a Canonical and Non-Canonical Translation Initiation Switch.

The replication of viruses requires host cell functions, specifically for protein synthesis, as viruses lack their own translational machinery. Failure to translate viral mRNAs and generate viral proteins would affect the propagation and evolution of a virus. Thus, independently of their size, complexity, and genomes, viruses evolved sophisticated molecular mechanisms to hijack the translational apparatus of a host in order to recruit ribosomes for efficient protein production. One of the prevalent mechanisms of translation regulation utilized by viruses is non-canonical translation initiation. It is often governed by the 5'-untranslated regions (5'-UTRs) present upstream of a protein-coding sequence in viral mRNAs, such as internal ribosome entry sites (IRESs) and capindependent translation enhancers (CITEs). Viruses can also utilize canonical translation initiation factors of a host in non-canonical ways. Understanding strategies and mechanisms used by viruses to generate proteins is an important task, as it might help develop new therapeutic interventions. We previously have demonstrated that mRNA from the genome of the black beetle virus (BBV) of the