1. S. K. Choi, J. H. Lee, T. E. Dever, Laboratory of Eukaryotic Gene Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892–2716, USA.
2. W. L. Zoll and W. C. Merrick, Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA.