9 Department of Structural and Computational Biology, Center for Molecular Biology, University of Vienna, Vienna, Austria. sebastian.falk@univie.ac.at.
10 Biology of Non-coding RNA group, Institute of Molecular Biology, Mainz, Germany. r.ketting@imb-mainz.de.
11 Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Mainz, Germany. r.ketting@imb-mainz.de.