The seven canonical Sm proteins of <I>Saccharomyces cerevisiae</I> associate with the U1, U2, U4 and U5 spliceosomal snRNAs, and have roles in the biogenesis and localisation of these snRNP particles. The proteins interact extensively with one another in an ordered pathway. In contrast, the Uss1 protein is a non-canonical member of the Sm-like protein family in that it associates with the U6 snRNA. A combination of molecular genetic and biochemical analysis has been used to investigate the molecular associations of the Uss1 protein. Exhaustive two-hybrid screens revealed interactions with other Sm-like proteins, with proteins of the U2 snRNP (and proteins interacting with U2 snRNP proteins) and with proteins not previously reported to be involved in pre-mRNA splicing. A network of potential interactions was produced from these data. Deletion of six open reading frames (ORFs) encoding Sm-like proteins revealed three as essential for cell viability (YBL026w, YER146w and <I>USS2</I>) and three as non-essential (<I>SPB8, </I>YDR378c and YNL147w) suggesting functional redundancies within these non-canonical Sm-like proteins. Since significant levels of U6 snRNA can be precipitated with all 6 proteins, and the Yjr022p (an Sm-like protein identified in two-hybrid screens) the genes encoding these proteins were added to the <I>USS</I> (<I>U</I>-<I>S</I>ix <I>S</I>nRNP) gene class. A subset of these proteins is essential for the stability of U6 snRNA <I>in vivo</I>, with over-production of U6 capable of (partially) rescuing the growth of the conditional strains. All 7 Sm-like proteins which associate with U6 snRNA also co-immunoprecipitate with Uss1p. This combined with the range of interactions revealed by two-hybrid analyses suggests the existence of an Sm-like protein complex (or complexes).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:657486 |
| Date | January 1998 |
| Creators | Mayes, Andrew Easson |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15298 |
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