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This article has been peer reviewed. It was published in: RNA.

Volume 21, Issue 4, 1 April 2015, Pages 642-644.

The published version is available at DOI: 10.1261/rna.049825.115

Copyright © 2015 Hou et al. This article, published in RNA, is available under a Creative Commons License (Attribution-NonCommercial 4.0 Inter-national), as described at

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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