Blooms Like It Hot

RNA pieces in the spliceosome, has a domain V counterpart, containing a 2-nucleotide bulge located 5 base pairs away from an AGC triad (10). Formation of an analogous metalbinding platform in this region of U6 (11) may explain the apparent ability of spliceosomal RNAs to retain catalytic activity in the complete absence of the many protein components that usually accompany splicing (12). A domain V-like element could have played a major role during the RNA world era of evolution, serving as the catalytic center for RNA cleavage, transesterification, and polymerization reactions. The new structure provides a powerful starting point for future investigations of group II introns and the spliceosome. The