1. Laboratory for Computational Biology and Bioinformatics, School of Computer and Communication Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
2. Swiss Institute of Bioinformatics, Lausanne, Switzerland
3. Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Israel
4. Faculty of Mathematics and Computer Science, Weizmann Institute of Science, Rehovot, Israel
5. Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, IsraelZhang and Tuller have contributed equally to this work