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Molecular and Cellular Biology, December 2000, p. 9028-9040, Vol.
20, No. 23
Friedrich-Miescher Institut, CH-4058 Basel, Switzerland
Received 27 July 2000/Returned for modification 30 August
2000/Accepted 12 September 2000
The H/ACA small nucleolar RNAs (snoRNAs) are involved in pseudouridylation
of pre-rRNAs. In the yeast Saccharomyces cerevisiae, four common proteins are
associated with H/ACA snoRNAs: Gar1p, Cbf5p, Nhp2p, and Nop10p. In vitro
reconstitution studies showed that four proteins also specifically interact with
H/ACA snoRNAs in mammalian cell extracts. Two mammalian proteins, NAP57/dyskerin
(the ortholog of Cbf5p) and hGAR1, have been characterized. In this work we
describe properties of hNOP10 and hNHP2, human orthologs of yeast Nop10p and Nhp2p,
respectively, and further characterize hGAR1. hNOP10 and hNHP2 complement yeast
cells depleted of Nhp2p and Nop10p, respectively. Immunoprecipitation experiments with
extracts from transfected HeLa cells indicated that epitope-tagged hNOP10 and
hNHP2 specifically associate with hGAR1 and H/ACA RNAs; they also interact with
the RNA subunit of telomerase, which contains an H/ACA-like domain in its 3' moiety.
Immunofluorescence microscopy experiments showed that hGAR1, hNOP10, and hNHP2 are localized
in the dense fibrillar component of the nucleolus and in Cajal (coiled) bodies. Deletion
analysis of hGAR1 indicated that its evolutionarily conserved core domain contains all the
signals required for localization, but progressive deletions from either the N or the C
terminus of the core domain abolish localization in the nucleolus and/or the Cajal bodies.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Human H/ACA Small Nucleolar RNPs and Telomerase
Share Evolutionarily Conserved Proteins NHP2 and NOP10
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and
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Corresponding author. Mailing address: Friedrich Miescher Institut, Maulbeerstrasse 66, CH-4058 Basel, Switzerland. Phone: 41 61 697 4128. Fax: 41 61 697 3976. E-mail: Witold.Filipowicz{at}fmi.ch.
Present address: Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT
06520-8040.
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