Key result
In Rice tungro bacilliform virus, ribosome shunting depends on the first short open reading frame followed by strong secondary structure, demonstrating evolutionary conservation in plant pararetroviruses.
The mechanism of ribosome shunting, which depends on a short ORF followed by a strong secondary structure, is evolutionarily conserved in plant pararetroviruses.
Does not change cardiovascular practice; extends shunting conservation to another plant pararetrovirus while leaving broader relevance open.
In plant pararetroviruses, pregenomic RNA serves both as a template for replication through reverse transcription and a polysictronic mRNA. This RNA has a complex leader sequence preceding the first large ORF. The leader contains multiple short ORFs and strong secondary structure, both inhibiting ribosome scanning. Translation on this RNA is initiated by shunting, in which scanning ribosomes bypass a large portion of the leader with the inhibitory secondary structure and short ORFs. In Cauliflower mosaic virus (CaMV), the ribosome shunting mechanism involves translation of the 5'-proximal short ORF terminating in front of the secondary structure that appears to force ribosomes to take off and resume scanning at a landing site downstream of the structure. Using two plant protoplast systems and shunt-competent wheat-germ extracts, we demonstrate that in Rice tungro bacilliform virus (RTBV) shunting also depends on the first short ORF followed by strong secondary structure. Swapping of the conserved shunt elements between CaMV and RTBV revealed the importance of nucleotide composition of the landing sequence for efficient shunting. The results suggest that the mechanism of ribosome shunting is evolutionary conserved in plant pararetroviruses.
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Pooggin et al. (2006) studied Rice tungro bacilliform virus (RTBV) translation. Mutations in RTBV leader sequence vs. Wild-type RTBV leader sequence was evaluated on Relative CAT reporter expression. In Rice tungro bacilliform virus, ribosome shunting depends on the first short open reading frame followed by strong secondary structure, demonstrating evolutionary conservation in plant pararetroviruses.