Interaction of the U3-55k protein with U3 snoRNA is mediated by the box B/C motif of U3 and the WD repeats of U3-55k.
U3 small nucleolar RNA (snoRNA) is a member of the Box C/D family of snoRNAs which functions in ribosomal RNA processing. U3-55k is a protein that has been found to interact with U3 but not other members of the Box C/D snoRNA family. We have found that interaction of the U3-55k protein with U3 RNA in vivo is mediated by the conserved Box B/C motif which is unique to U3 snoRNA. Mutation of Box B and Box C, but not of other conserved sequence elements, disrupted interaction of U3-55k with U3 RNA. Furthermore, a fragment of U3 containing only these two conserved elements was bound by U3-55k in vivo. RNA binding assays performed in vitro indicate that Box C may be the primary determinant of the interaction. We have cloned the cDNA encoding the Xenopus laevis U3-55k protein and find strong homology to the human sequence, including six WD repeats. Deletion of WD repeats or sequences near the C-terminus of U3-55k resulted in loss of association with U3 RNA and also loss of localization of U3-55k to the nucleolus, suggesting that protein-protein interactions contribute to the localization and RNA binding of U3-55k in vivo.
Lukowiak
A A
AA
Department of Biochemistry and Molecular Biology and Department of Genetics, University of Georgia, Life Science Building, Athens, GA 30602, USA.
Granneman
S
S
Mattox
S A
SA
Speckmann
W A
WA
Jones
K
K
Pluk
H
H
Venrooij
W J
WJ
Terns
R M
RM
Terns
M P
MP
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D020537:RNA, Small Nucleolar / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D020718:Ribonucleoproteins, Small Nucleolar / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D020537:RNA, Small Nucleolar; C117378:RNA, U3 small nucleolar; D011994:Recombinant Proteins; D020718:Ribonucleoproteins, Small Nucleolar; C117377:ribonucleoprotein, U3 small nucleolar