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Journal of Virology, March 2008, p. 3045-3053, Vol. 82, No. 6
0022-538X/08/$08.00+0     doi:10.1128/JVI.02390-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

cis- and trans-Acting Functions of Brome Mosaic Virus Protein 1a in Genomic RNA1 Replication{triangledown}

Guanghui Yi and Cheng Kao*

Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843

Received 5 November 2007/ Accepted 19 December 2007

RNA viruses employ a combination of mechanisms to regulate their gene expression and replication. Brome mosaic virus (BMV) is a tripartite positive-strand RNA virus used to study the requirements for virus infection. BMV genomic RNA1 encodes protein 1a, which contains a methyltransferase (MT) domain and a helicase domain that are required for replication. 1a forms a complex with the 2a RNA-dependent RNA polymerase for the replication and transcription of all BMV RNAs. RNA1 expressed with 2a from Agrobacterium-based vectors can result in RNA1 replication in Nicotiana benthamiana. A mutation in the 1a translation initiation codon significantly decreased RNA1 accumulation even when wild-type (WT) 1a and 2a were provided in trans. Therefore, efficient RNA1 replication requires 1a translation from RNA1 in cis, indicating a linkage between replication and translation. Mutation analyses showed that the full-length 1a protein was required for efficient RNA1 replication, not just the process of translation. Three RNA1s with mutations in the 1a MT domain could be partially rescued by WT 1a expressed in trans, indicating that the cis-acting function of 1a was retained. Furthermore, an RNA motif in the 5'-untranslated region of RNA1, named the B box, was required for 1a to function in cis and in trans for BMV RNA accumulation. The B box is required for the formation of the replication factory (M. Schwartz, J. Chen, M. Janda, M. Sullivan, J. den Boon, and P. Ahlquist, Mol. Cell 9:505-514, 2002). Results in this work demonstrate a linkage between BMV RNA1 translation and replication.

* Corresponding author. Mailing address: Department of Biochemistry and Biophysics, Texas A&M University, Mail Stop 2128, College Station, TX 77843. Phone: (979) 458-2235. Fax: (979) 845-9274. E-mail: ckao{at}tamu.edu

{triangledown} Published ahead of print on 26 December 2007.

Journal of Virology, March 2008, p. 3045-3053, Vol. 82, No. 6
0022-538X/08/$08.00+0     doi:10.1128/JVI.02390-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Yi, G., Letteney, E., Kim, C.-H., Kao, C. C. (2009). Brome mosaic virus capsid protein regulates accumulation of viral replication proteins by binding to the replicase assembly RNA element. RNA 15: 615-626 [Abstract] [Full Text]  


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