9304672 Maxwell Eukaryotic small nuclear RNAs(snRNAs) play critical roles in the processing of both pre-messenger and pre-ribosomal RNAs. One such nucleolar snRNA designated U14 snRNA is essential for the processing of pre-ribosomal RNA. The evolutionarily conserved ability of fungal, amphibian and mammalian U14 snRNAs to intermolecularly base-pair with 18SrRNA suggests that this hydrogen-bonding interaction is important in U14 snRNA function and ribosomal RNA processing events. We have demonstrated that the mouse U14 snRNA genes are located within introns 5,6 and 8 of the constitutively-expressed cognate hsc70 heat shock gene, a positioning which led to experiments confirming that an intron- processing pathway for U14 snRNA production exists. This is the first example of a eukaryotic pre-mRNA intron which is processed to yield a stable, biologically functional RNA species. We will continue characterizing U14 snRNA synthesis, structure and function while exploring the evolutionary conservation of those parameters. The processing sequences/structures essential for U14 snRNA excision will be determined by several different approaches. We will examine the developmental expression of U14 snRNA/hsc70 pre- mRNA in Xenopus laevis. We will examine the genomic organization of U14 snRNA genes in evolutionarily diverse eukaryotic organisms. %%% RNA is utilized both as a structural molecule for protein synthesis as well as a messenger molecule in the same process. Smaller RNA species have been found to be essential to the correct synthesis of the ribosomal and messenger RNAs and a number of them have been isolated and characterized. U14 snRNA is one such molecule, but one which is unique in that it was found by this laboratory to be located in introns of another gene, the hsc70 heat shock gene. This is the first example of an intron which is processed to yield a stable, biologically functional RNA species. The process of producing the U14 snRNA will be studied more extensiv ely as well as the developmental expression and the evolutionary conservation of this RNA species. ***
