Mol Cell Biol, August 1998, p. 4409-4417, Vol. 18, No. 8
Department of Microbiology and Immunology,
UCLA School of Medicine, Los Angeles, California
90095-17471;
Biochemistry & Molecular
Biology, Albany Medical College, Albany, New York
122082; and
Program in Molecular
Pathogenesis, University of California, San Francisco, California
94143-04223
Received 24 February 1998/Returned for modification 29 April
1998/Accepted 1 May 1998
First characterized in Trypanosoma brucei, the spliced
leader-associated (SLA) RNA gene locus has now been isolated from the kinetoplastids Leishmania tarentolae and Trypanosoma
cruzi. In addition to the T. brucei SLA RNA, both
L. tarentolae and T. cruzi SLA RNA repeat units
also yield RNAs of 75 or 76 nucleotides (nt), 92 or 94 nt, and ~450
or ~350 nt, respectively, each with significant sequence identity to
transcripts previously described from the T. brucei SLA RNA
locus. Cell fractionation studies localize the three additional RNAs to
the nucleolus; the presence of box C/D-like elements in two of the
transcripts suggests that they are members of a class of small
nucleolar RNAs (snoRNAs) that guide modification and cleavage of rRNAs.
Candidate rRNA-snoRNA interactions can be found for one domain in each
of the C/D element-containing RNAs. The putative target site for the
75/76-nt RNA is a highly conserved portion of the small subunit rRNA
that contains 2'-O-ribose methylation at a conserved
position (Gm1830) in L. tarentolae and in vertebrates. The
92/94-nt RNA has the potential to form base pairs near a conserved
methylation site in the large subunit rRNA, which corresponds to
position Gm4141 of small rRNA 2 in T. brucei. These data
suggest that trypanosomatids do not obey the general 5-bp rule for
snoRNA-mediated methylation.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Three Small Nucleolar RNAs Identified from the
Spliced Leader-Associated RNA Locus in Kinetoplastid
Protozoans
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, UCLA School of Medicine, 10833 Le Conte Ave., Los Angeles, CA 90095-1747. Phone: (310) 825-4195. Fax: (310)
206-3865. E-mail: dc{at}ucla.edu.
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