1. Department of Macromolecular Science and the Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, People's Republic of China; Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK; Department of Zoology, University of Aarhus, Universitetsparken B135, 8000 Aarhus C, Denmark; and Laboratory of Gene Expression, University of Aarhus, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark