[1] Univ Calif Berkeley, Dept Mol & Cell Biol, Berkeley, CA 94720 USA
[2] Univ Calif Berkeley, Ctr Computat Biol, Berkeley, CA 94720 USA
[3] Tel Aviv Univ, Dept Stat & Operat Res, IL-69978 Tel Aviv, Israel
[4] Univ Calif Berkeley, Dept Nutr Sci & Toxicol, Berkeley, CA 94720 USA