Three yeast snRNAs (snR20, snR7, and snR14) have been implicated in pre-mRNA splicing. snR20 and snR7 contain domains of homology to U2 and U5, respectively, and each is required for viability. These RNAs are found associated with the spliceosome, as is snR14. We show here that snR14 is also an essential gene product. Sequence analysis reveals that, like snR7 and snR20, snR14 contains a consensus binding site for the Sm antigen, a feature common to all mammalian snRNAs involved in splicing. Moreover, snR14 exhibits several blocks of sequence and structural homology to U4, which in metazoans is found in association with U6. Native gel electrophoresis demonstrates that snR14 is in fact base-paired with another yeast snRNA, designated snR6, which has primary sequence homology to U6. We conclude that snR14 is the yeast analog of U4.
Bibliographical noteFunding Information:
We thank Ram Reddy for the mouse U6 clone, and Laura Christensen for synthesizing the oligonucieotides used in the work. We are grateful to L. Esperas for technical assistance, to E. Shuster and M. Jones for comments, and to J. Piccini for preparing the manuscript. This work was supported by grants from the National Institutes of Health (GM21119) and the National Science Foundation (DCB-8603926) to C. G. P G. S. was supported by a Damon Runyon-Walter Winchell Cancer Fund fellowship, DRG-872. D. A. 8. was supported an American Cancer Society fellowship, PF-2816.