Abstract
Retrotransposons and repetitive DNA elements in eukaryotes are silenced by small RNA–directed heterochromatin formation. In Arabidopsis, this process involves 24-nt siRNAs that bind to ARGONAUTE4 (AGO4) and facilitate the targeting of complementary loci1,2 via unknown mechanisms. Nuclear RNA polymerase V (Pol V) is an RNA silencing enzyme recently shown to generate noncoding transcripts at loci silenced by 24-nt siRNAs3. We show that AGO4 physically interacts with these Pol V transcripts and is thereby recruited to the corresponding chromatin. We further show that DEFECTIVE IN MERISTEM SILENCING3 (DMS3), a structural maintenance of chromosomes (SMC) hinge-domain protein4, functions in the assembly of Pol V transcription initiation or elongation complexes. Collectively, our data suggest that AGO4 is guided to target loci through base-pairing of associated siRNAs with nascent Pol V transcripts.
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Acknowledgements
Our work is supported by US National Institutes of Health grant GM077590. The content of the paper is the sole responsibility of the authors and does not necessarily reflect the views of the NIH. We thank T. Blevins (Washington University, St. Louis), S. Jacobsen (University of California, Los Angeles) and T. Jenuwein (Max Planck Institute of Immunobiology) for providing reagents.
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T.S.R. generated anti-AGO4; J.R.H. and T.S.R. assayed NRPE1–AGO4 interactions; J.R.H. produced Figure 4d; A.T.W. performed all remaining experiments. A.T.W. and C.S.P. wrote the manuscript.
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Wierzbicki, A., Ream, T., Haag, J. et al. RNA polymerase V transcription guides ARGONAUTE4 to chromatin. Nat Genet 41, 630–634 (2009). https://doi.org/10.1038/ng.365
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DOI: https://doi.org/10.1038/ng.365
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