ACKNOWLEDGMENTS
We thank our many colleagues who have contributed unpublished results to this review, and we apologize to all those whose work could not be cited owing to space limitations. We are grateful to K. Tanner, D. Tollervey, and J. Venema for stimulating discussions and R. Boeck and K. Tanner for critical reading of the manuscript. J.D.L.C. thanks A. Vioque for encouragement.
The work in the authors’ laboratory was funded by grants from the Swiss National Science Foundation and the University of Geneva to P.L. We gratefully acknowledge C. Georgopoulos for support. J.D.L.C. thanks the MEC (Spain) for financial support.