About the Authors
Crick-Jacobs Center for Theoretical and Computational Biology, Salk Institute, La Jolla, California, United States of America
Laboratory of Genetics, Salk Institute, La Jolla, California, United States of America
The authors have declared that no competing interests exist.
GWY conceived and designed the experiments. GWY, ELVN, and TYL performed the experiments. GWY and ELVN analyzed the data. GWY wrote the paper.