.:/ 1992 Oxford University Press

3518 Nucleic Acids Research, Vol. 20, No. 13

Sequence of a new snRNA from the ciliate Tetrahymena therrmophila Henrik Orum, Henrik Nielsen1 and Jan Engberg The Royal Danish School of Pharmacy, Department of Biology, 2 Universitetsparken, DK-2100 Copenhagen and 'Department of Biochemistry B, The Panum Institute, University of Copenhagen, 3 Blegdamsvej, DK-2200 Copenhagen, Denmark EMBL accession no. X65863

Submitted May 19, 1992 We have previously characterized the T thernophila homologues of the major mammalian U-snRNAs, Ul to U6 (1 and unpublished data). During this work a new snRNA species was reproducibly recovered in the nuclear fraction. The sequence of this snRNA was established by direct chemical sequencing (2) followed by dideoxy-sequencing using primers complementary to the chemically detennined sequence at the 3' end. Furthermore, the 3' end of the snRNA was mapped by the previously described reverse dideoxy sequencing method (1). The combined sequence data defines an snRNA with a total size of 99 nt with unique 5' and 3' ends. We have termed this snRNA Tx-i. The sequence of the Tx-i snRNA displays no significant overall similarity to other published snRNAs. It does, however, contain two small sequence motifs that matches the phylogenetically conserved box C (cons.: AG/U,PyGAUGA (3)) and D (cons.: PuUCUGA (4)) motifs of nucleolar snRNAs, U3 (3), U8 and U13 (4) and U14 (5). Moreover, the putative box D of the Tx-I snRNA occurs at the phylogenetically conserved position (4) a few nucleotides from the 3' end. We therefore analyzed whether the sequence of the Tx-I snRNA could be folded into a secondary structure model resembling those proposed for the nucleolar U8 and U13 (4) and U14-snRNAs (5). This, however, was not possible. Furthermore, no alternative secondary structures of the

U8, U13 and U14 snRNAs appear to be compatible with the sequence of the Tx-i snRNA and vice versa. Thus, we believe that the Tx-i snRNA represents a novel snRNA species.

REFERENCES 1. 0rum,H., Nielsen,H. and Engberg,J. (1991) J. Mol. Biol. 222, 219-232. 2. Peattie,D.A. (1979) Proc. Natl. Acad Sci. USA 76, 1760-1764. 3. Jeppesen,C., Stebbins-Boaz,B. and Gerbi,S. (1988) Nucleic Acid Res. 16, 2127-2149. 4. Tyc,K. and Steitz,J.A. (1989) EMBO J. 8, 3113-3119. 5. Li,V.H., Zagorski,J. and Fournier,M.J. (1990) Mol. Cell. Biol. 10, 1145-1152.

5' NAACATGATG

TATMMACGC ATGGAAAGAG GITIGTAGTT MCCCTACTG

AACCCAGGGT TMGCCATCC CTOGATGMT CCATACCMT CGTCTGATT- 3' Box C Box D

Figure 1. The sequence of the T.thermophila Tx-I snRNA. The putative box C and D sequence motifs are underlined. The N at the 5' end of the sequence indicates that the identity of this nucleotide has not been determined.

Sequence of a new snRNA from the ciliate Tetrahymena thermophila.

:/ 1992 Oxford University Press 3518 Nucleic Acids Research, Vol. 20, No. 13 Sequence of a new snRNA from the ciliate Tetrahymena therrmophila Henr...
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