Short ORF-Dependent Ribosome Shunting Operates in an RNA Picorna-Like Virus and a DNA Pararetrovirus that Cause Rice Tungro Disease

PLoS Pathogens

Lyubov A. Ryabova¹  Mikhail V. Schepetilnikov¹  Mikhail M. Pooggin²  Rajendran Rajeswaran² 

[1] Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France;Institute of Botany, University of Basel, Basel, Switzerland

关键词: Ribosomes;    Protein translation;    Point mutation;    Sequence motif analysis;    Translation initiation;    RNA stem-loop structure;    Gene prediction;    Rice;   

DOI  :  10.1371/journal.ppat.1002568

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Rice tungro disease is caused by synergistic interaction of an RNA picorna-like virus Rice tungro spherical virus (RTSV) and a DNA pararetrovirus Rice tungro bacilliform virus (RTBV). It is spread by insects owing to an RTSV-encoded transmission factor. RTBV has evolved a ribosome shunt mechanism to initiate translation of its pregenomic RNA having a long and highly structured leader. We found that a long leader of RTSV genomic RNA remarkably resembles the RTBV leader: both contain several short ORFs (sORFs) and potentially fold into a large stem-loop structure with the first sORF terminating in front of the stem basal helix. Using translation assays in rice protoplasts and wheat germ extracts, we show that, like in RTBV, both initiation and proper termination of the first sORF translation in front of the stem are required for shunt-mediated translation of a reporter ORF placed downstream of the RTSV leader. The base pairing that forms the basal helix is required for shunting, but its sequence can be varied. Shunt efficiency in RTSV is lower than in RTBV. But in addition to shunting the RTSV leader sequence allows relatively efficient linear ribosome migration, which also contributes to translation initiation downstream of the leader. We conclude that RTSV and RTBV have developed a similar, sORF-dependent shunt mechanism possibly to adapt to the host translation system and/or coordinate their life cycles. Given that sORF-dependent shunting also operates in a pararetrovirus Cauliflower mosaic virus and likely in other pararetroviruses that possess a conserved shunt configuration in their leaders it is tempting to propose that RTSV may have acquired shunt cis-elements from RTBV during their co-existence.

【 授权许可】

CC BY