Fibrillarin binds directly and specifically to U16 box C/D snoRNA

Eukaryotic nucleoli contain a large family of box C/D small nucleolar ribon ucleoprotein complexes (snoRNPs) that are involved in processing and site-s pecific methylation of pre-rRNA, Several proteins have been reported to be common factors of box C/D snoRNPs in lower and higher eukaryotes; neverthel ess none of them has been clearly shown to directly interact with RNA. We p reviously identified in Xenopus laevis, by means of UV crosslinking in vivo , two proteins associated with box C/D snoRNAs, fibrillarin and p68, Here w e show that fibrillarin interacts directly and specifically with the U16 bo x CID snoRNA in a X. laevis oocyte nuclear extract and that it does not req uire p68 for binding. Specific binding is also obtained with a recombinant fibrillarin demonstrating that the protein is able to bind directly and spe cifically to U16 snoRNA by itself.