Box C/D small nucleolar RNAs (snoRNAs) direct site-specific methylation of ribose 2′-hydroxyls in ribosomal and spliceosomal RNAs. To identify snoRNA functional groups contributing to assembly of an active box C/D snoRNP in Xenopus oocytes, we developed an in vivo nucleotide analog interference mapping procedure. Deleterious substitutions consistent with requirements for binding the 15.5 kD protein clustered within the terminal box C/D motif only. In vitro analyses confirmed a single interaction site for recombinant 15.5 kD protein and identified the exocyclic amine of A89 in box D as essential for binding. Our results argue that the 15.5 kD protein interacts asymmetrically with the two sets of conserved box C/D elements and that its binding is primarily responsible for the stability of box C/D snoRNAs in vivo.
Szewczak, L. B. W., DeGregorio, S. J., Strobel, S. A., & Steitz, J. A. (2002). Exclusive interaction of the 15.5 kD protein with the terminal box C/D motif of a methylation guide snoRNP. Chemistry and Biology, 9(10), 1095–1107. https://doi.org/10.1016/S1074-5521(02)00239-9