The poly(A) tail blocks RDR6 from converting self mRNAs into substrates for gene silencing

Abstract

It remains unclear how post-transcriptional gene silencing (PTGS) in plants discriminates aberrant RNAs from canonical messenger RNAs (mRNAs). The key step of plant PTGS is the conversion of aberrant RNAs into double-stranded RNAs by RNA-DEPENDENT RNA POLYMERASE6 (RDR6). Here, we show that RDR6 itself selects aberrant poly(A)-less mRNAs over canonical polyadenylated mRNAs as templates at the initiation step of complementary strand synthesis. This mechanism can be viewed as an innate safeguard against ‘self-attack’ by PTGS.

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Figure 1: AtRDR6 has an intrinsic preference for poly(A)-less mRNAs over polyadenylated mRNAs as templates.
Figure 2: Poly(A) tail inhibits the initiation step of complementary strand synthesis by AtRDR6.

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Acknowledgements

We are grateful to members of Tomari laboratory for discussion and technical support. This work was supported in part by Grants-in-Aid for Scientific Research on Innovative Areas (‘Non-coding RNA neo-taxonomy’) 26113007 (to Y.T.) and (‘Nascent-chain Biology’) 26116003 (to H.I), Grant-in-Aid for Young Scientists (A) 16H06159 (to H.I.), Grant-in-Aid for Challenging Exploratory Research 15K14444 (to H.I.) and Grant-in-Aid for JSPS Fellows 16J07290 (to K.B.).

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K.B. performed all experiments. H.I. and Y.T. supervised the project. K.B., H.I. and Y.T. wrote the manuscript.

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Correspondence to Hiro-oki Iwakawa or Yukihide Tomari.

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The authors declare no competing financial interests.

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Supplementary Figures 1-4, Supplementary Methods, Supplementary References, Supplementary Table 1. (PDF 728 kb)

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Baeg, K., Iwakawa, H. & Tomari, Y. The poly(A) tail blocks RDR6 from converting self mRNAs into substrates for gene silencing. Nature Plants 3, 17036 (2017). https://doi.org/10.1038/nplants.2017.36

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