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