Nature 403, 672— 676 (2000).

The fourth sentence in the Methods section should have read “For stimulation experiments, HEL (Sigma) was used at 500 ng ml-1, goat anti-mu (Jackson Labs) at 10 µg ml-1, FK506 (gift from G. Crabtree laboratory) at 10 ng ml-1, PD98059 (NEB) at 20 µM unless otherwise stated, ionomycin (gift from G. Crabtree laboratory) at 1 µM and EGTA at 3 mM.”