Deciphering the mechanism of defective interfering RNA (DI RNA) biogenesis reveals that a viral protein and the DI RNA act antagonistically in virus infection.

Abstract

Potato mop-top virus (PMTV) produces a defective RNA (D RNA) encompassing the 5'-terminal 479 nucleotides (nt) and 3'-terminal 372 nt of RNA-TGB (where TGB is triple gene block). The mechanism that controls D RNA biogenesis and the role of D RNA in virus accumulation was investigated by introducing deletions, insertions, and point mutations into the sequences of the open reading frames (ORFs) of TGB1 and the 8-kilodalton (8K) protein that were identified as required for efficient production of the D RNA. Transient expression of RNA-TGB in the absence of RNA-Rep (which encodes the replicase) did not result in accumulation of D RNA, indicating that its production is dependent on PMTV replication. The D RNA could be eliminated by disrupting a predicted minus-strand stem-loop structure comprising complementary sequences of the 5' TGB1 ORF and the 3' 8K ORF, suggesting intramolecular template switching during positive-strand synthesis as a mechanism for the D RNA biogenesis. Virus accumulation was reduced when the 8K ORF was disrupted but D RNA was produced. Conversely, the virus accumulated at higher titers when the 8K ORF was intact and D RNA production was blocked. These data demonstrate that the D RNA interferes with virus infection and therefore should be referred to as a defective interfering RNA (DI RNA). The 8K protein was shown to be a weak silencing suppressor. This study provides an example of the interplay between a pathogen and its molecular parasite where virus accumulation was differentially regulated by the 8K protein and DI RNA, indicating that they play antagonistic roles and suggesting a mechanism by which the virus can attenuate replication, decreasing viral load and thereby enhancing its efficiency as a parasite.

• Authors: Nina I Lukhovitskaya, Srinivas Thaduri, Sonya K Garushyants, Lesley Torrance, Eugene I Savenkov
• Journal: Journal of virology (J Virol) Vol. 87 Issue 11 Pg. 6091-103 (Jun 2013) ISSN: 1098-5514 [Electronic] United States
• PMID: 23514891 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• RNA, Viral
• Viral Proteins

Topics

• Base Sequence
• Defective Viruses (chemistry, genetics, metabolism)
• Humans
• Inverted Repeat Sequences
• Molecular Sequence Data
• Open Reading Frames
• Plant Diseases (virology)
• RNA Interference
• RNA Viruses (chemistry, genetics, metabolism)
• RNA, Viral (chemistry, genetics, metabolism)
• Tobacco (virology)
• Viral Proteins (chemistry, genetics, metabolism)