Enhancement of RNA synthesis by promoter duplication in tombusviruses

T. Panavas, Z. Panaviene, J. Pogany, P. D. Nagy

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Replication of tombusviruses, small plus-strand RNA viruses of plants, is regulated by cis-acting elements present in the viral RNA. The role of cis-acting elements can be studied in vitro by using a partially purified RNA-dependent RNA polymerase (RdRp) preparation obtained from tombusvirus-infected plants (Nagy, P.D., and Pogany, J. 2000, Virology 276, 279- 288). Here, we demonstrate that the minus-strand RNA of tombusviruses contains, in addition to the 3′-terminal minimal plus-strand initiation promoter, a second cis-acting element, termed the promoter proximal enhancer (PPE). The PPE element enhanced RNA synthesis by almost threefold from the adjacent minimal promoter in the in vitro assay. The sequence of the PPE element is 70% similar to the minimal promoter, suggesting that sequence duplication of the minimal promoter may have been the mechanism leading to the generation of the PPE. Consistent with this proposal, replacement of the PPE element with the minimal promoter, which resulted in a perfectly duplicated promoter region, preserved its enhancer-like function. In contrast, mutagenesis of the PPE element or its replacement with an artificial G/C-rich sequence abolished its stimulative effect on initiation of RNA synthesis in vitro. In vivo experiments are also consistent with the role of the PPE element in enhancement of tombusvirus replication. Sequence comparison of several tombusviruses and related carmoviruses further supports the finding that duplication of minimal promoter sequences may have been an important mechanism during the evolution of cis-acting elements in tombusviruses and related RNA viruses.

Original languageEnglish
Pages (from-to)118-129
Number of pages12
Issue number1
StatePublished - May 25 2003

Bibliographical note

Funding Information:
This work was supported by NSF (MCB0078152) and by the University of Kentucky. This study is Publication No. 02-12-017 of the Kentucky Agricultural Experiment Station.


  • Plus-strand synthesis
  • Protoplast
  • RNA enhancer
  • RNA promoter
  • Replication
  • de novo initiation

ASJC Scopus subject areas

  • Virology


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