Articles
3′ TERMINAL SEQUENCE OF BLACKCURRANT REVERSION VIRUS (BRV) RNA2 ARE HIGHLY CONSERVED IN DIFFERENT VIRUS ISOLATES, AND AFFECT ITS TRANSLATIONAL EFFICIENCY
Article number
656_16
Pages
109 – 114
Language
English
Abstract
Blackcurrant reversion virus (BRV) belongs to the subgroup c of Nepoviruses. A specific feature of BRV, and of other subgroup c nepoviruses is the long 3′ non-translated regions (3′ NTR) of the genomic RNAs (1360 and 1363 nucleotides for RNAs1 and 2, respectively). The 3′ NTRs sequences are highly conserved between the RNAs 1 and 2 of the isolated type strain, as well as between ten field isolates originating from different Ribes hosts and from very different geographic locations.
On the secondary structure level, four conserved stem- loops in the RNAs 1 and 2 of the type strain, as well as in the 3′ NTRs of all of the analysed field isolates, and three slightly less-conserved stem-loop structures were identified by the M-fold analysis.
A set of nested deletions was created in the 3′ terminus of BRV RNA2 to delete these structures or the entire 3′ NTR in a progressive manner, in order to test their effects on the translational efficiency of BRV RNA2. The transcripts of the full-length or 3′ truncated RNA2 constructs were optionally 5′ capped, and/or poly(A)-tailed, and translated in two different translation systems.
So far, translation of the full-length RNA2-encoded polypeptides has not been obtained from these templates, indicating that their translation is initiated only internally in the transcripts, or it is prematurely terminated.
However, the deletions enhanced the translation of the less-than-full-length products, in a progressive manner, from the uncapped, non-poly(A)-tailed transcripts.
The deletions reduced, in progressive manner, the translational efficiency of the 5′ capped transcripts, and in combination with poly(A)-tailing the effect was the opposite.
These results suggest that the 3′ NTR interferes with the translation initiation, and affects the regulatory role of both the 5′ cap and the poly(A) tail in this process.
On the secondary structure level, four conserved stem- loops in the RNAs 1 and 2 of the type strain, as well as in the 3′ NTRs of all of the analysed field isolates, and three slightly less-conserved stem-loop structures were identified by the M-fold analysis.
A set of nested deletions was created in the 3′ terminus of BRV RNA2 to delete these structures or the entire 3′ NTR in a progressive manner, in order to test their effects on the translational efficiency of BRV RNA2. The transcripts of the full-length or 3′ truncated RNA2 constructs were optionally 5′ capped, and/or poly(A)-tailed, and translated in two different translation systems.
So far, translation of the full-length RNA2-encoded polypeptides has not been obtained from these templates, indicating that their translation is initiated only internally in the transcripts, or it is prematurely terminated.
However, the deletions enhanced the translation of the less-than-full-length products, in a progressive manner, from the uncapped, non-poly(A)-tailed transcripts.
The deletions reduced, in progressive manner, the translational efficiency of the 5′ capped transcripts, and in combination with poly(A)-tailing the effect was the opposite.
These results suggest that the 3′ NTR interferes with the translation initiation, and affects the regulatory role of both the 5′ cap and the poly(A) tail in this process.
Authors
A. Karetnikov, M. Keränen, K. Lehto
Keywords
3′ NTR, RNA secondary structures, translation, translational regulation, closed loop model
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