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 |
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| Authors: | Lukowiak A A Granneman S Mattox S A Speckmann W A Jones K Pluk H Venrooij W J Terns R M Terns M P |
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| Affiliation: | Department of Biochemistry and Molecular Biology and Department of Genetics, University of Georgia, Life Science Building, Athens, GA 30602, USA. |
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| Abstract: | 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. |
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