Fig. 1. C. elegans histone hairpin-binding protein and the histone hairpin RNA sequence element. (A) C. elegans HBP sequence aligned with the RNA-binding domains (RBD) of other HBPs. Both the full-length protein and the RBD (underlined) bind to the C. elegans histone hairpin structure (Michel et al., 2000). (B) The conserved sequence element in the 3' untranslated region of histone genes encompassing the hairpin structure. Conserved residues in metazoan histone RNA hairpins are circled. C11 is unique to C. elegans histone RNAs. Nucleotide position numbering is arbitrary.