[1] Washington Univ, Sch Med, Dept Internal Med, St Louis, MO 63110 USA
[2] Washington Univ, Sch Med, Dept Mol Biol & Pharmacol, St Louis, MO 63110 USA
[3] Univ Calif Los Angeles, Dept Med, Los Angeles, CA 90024 USA
[4] Univ Calif Los Angeles, Dept Microbiol & Mol Genet, Los Angeles, CA 90024 USA
[5] Univ Calif Los Angeles, Inst Mol Biol, Los Angeles, CA 90024 USA