Nature 402, 489–495 (1999)

The names of the following authors were omitted from the complete list at the end of the Article: P. Wilkinson (The Sanger Centre, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK); A. Bodenteich, K. Hartman, X. Hu, A. S. Khan, L. Lane, Y. Tilahun & H. Wright (Department of Chemistry and Biochemistry, The University of Oklahoma, 620 Parrington Oval, Room 311, Norman, Oklahoma 73019, USA).