Ribosome Shunt in Adenovirus
Ribosome shunting is observed during expression of late adenovirus mRNAs. Late adenovirus mRNAs contains a 5’ tripartite leader, a highly conserved 200-nt NTR with a 25- to 44- nt unstructured 5’ conformation followed by a complex group of stable hairpin structure, which confers preferential translation by reducing the requirement for the eIF-4F (cap-binding protein complex), which is inactivated by adenovirus to interfere cellular protein translation. When eIF4E is abundant, both linear scanning and shunting are performed; however, when eIF4E is altered or deactivated during late adenovirus infection of heat shock, the tripartite leader exclusively and efficiently directs initiation by shunting.
In the case of adenovirus late mRNA and hsp70 mRNA, instead of recognition of stop codon of first short ORF, pausing of translation is caused by scanning ribosome with three conserved sequences that are complementary to the 3’ hairpin of 18S ribosomal RNA.
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