[1] IGBMC, Dept Integrated Struct Biol, Illkirch Graffenstaden, France
[2] Univ Michigan, Dept Chem, Ann Arbor, MI USA
[3] Univ Michigan, Ctr RNA Biomed, Ann Arbor, MI USA
[4] Tech Univ Berlin, Inst Biotechnol, Berlin, Germany
[5] Wellcome Ctr Cell Biol, Edinburgh, Midlothian, Scotland