In these viruses the ribosome is directly translocated from the upstream initiation complex to the start codon (AUG) without the need to unwind RNA secondary structures.
[2] The 35S RNA of CaMV contains a ~600 nucleotide leader sequence which contains 7-9 short open reading frames (sORFs) depending on the strain.
This long leader sequence has the potential to form an extensive complex stem-loop structure, which is an inhibitory element for expression of following ORFs.
The 40S ribosomal subunits keep combining with RNA, and bypass the strong stem-loop structural element, land at the shunt acceptor site, resume scanning and reinitiate at the first long ORF.
[7] The mechanism of ribosome shunting in RTBV resembles that in CaMV: it also requires the first short ORF as well as a following strong secondary structure.
Late adenovirus mRNAs contains a 5’ tripartite leader, a highly conserved 200-nucleotide NTR with a 25- to 44- nucleotide 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 with cellular protein translation.