Resistance of RNA-mediated TGS to HC-Pro, a viral suppressor of PTGS, suggests alternative pathways for dsRNA processing

M. F. Mette, A. J.M. Matzke, M. A. Matzke*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


In plants, double-stranded (ds) RNA that is degraded to small (sm) RNAs that are ∼23 nucleotides in length can trigger the degradation of homologous RNAs in the cytoplasm (posttranscriptional gene silencing or PTGS) and de novo methylation of homologous DNA in the nucleus [1]. PTGS is similar to quelling in fungi [2] and RNAi in animals [3]. RNA-directed DNA methylation (RdDM) can lead to transcriptional gene silencing (TGS) and the methylation of homologous target promoters if dsRNAs containing promoter sequences are involved [4]. HC-Pro is a plant viral suppressor of PTGS that acts by preventing the accumulation of smRNAs [5, 6] that provide the specificity determinant for homologous RNA degradation [7-10]. Here, we show that HC-Pro does not suppress TGS induced by promoter dsRNA. Moreover, the amount of promoter smRNAs is elevated 5-fold in the presence of HC-Pro, and target promoter methylation is slightly increased without a concomitant rise in the level of promoter dsRNA. The promoter dsRNA, which is not polyadenylated, failed to trigger substantial degradation of polyadenylated, single-stranded promoter RNA. The differential effects of HC-Pro on smRNA accumulation associated with dsRNA-mediated TGS and at least some cases of PTGS suggest that dsRNA processing can occur by alternative pathways, and they support the idea that RdDM is triggered by smRNAs.

Original languageEnglish (US)
Pages (from-to)1119-1123
Number of pages5
JournalCurrent Biology
Issue number14
StatePublished - Jul 24 2001
Externally publishedYes

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences


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