Originally published as Genetics Published Articles Ahead of Print on May 23, 2005.

Genetics, Vol. 170, 1063-1080, July 2005, Copyright © 2005
doi:10.1534/genetics.105.042044

Genetic Analysis Reveals a Role for the C Terminus of the Saccharomyces cerevisiae GTPase Snu114 During Spliceosome Activation

Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143-2200

1 Corresponding author: Department of Biochemistry and Biophysics, 600 16th St., Genentech Hall, San Francisco, CA 94143-2200.
E-mail: guthrie{at}biochem.ucsf.edu

Snu114 is the only GTPase required for mRNA splicing. As a homolog of elongation factor G, it contains three domains (III–V) predicted to undergo a large rearrangement following GTP hydrolysis. To assess the functional importance of the domains of Snu114, we used random mutagenesis to create conditionally lethal alleles. We identified three main classes: (1) mutations that are predicted to affect GTP binding and hydrolysis, (2) mutations that are clustered in 10- to 20-amino-acid stretches in each of domains III–V, and (3) mutations that result in deletion of up to 70 amino acids from the C terminus. Representative mutations from each of these classes blocked the first step of splicing in vivo and in vitro. The growth defects caused by most alleles were synthetically exacerbated by mutations in PRP8, a U5 snRNP protein that physically interacts with Snu114, as well as in genes involved in snRNP biogenesis, including SAD1 and BRR1. The allele snu114-60, which truncates the C terminus, was synthetically lethal with factors required for activation of the spliceosome, including the DExD/H-box ATPases BRR2 and PRP28. We propose that GTP hydrolysis results in a rearrangement between Prp8 and the C terminus of Snu114 that leads to release of U1 and U4, thus activating the spliceosome for catalysis.




This article has been cited by other articles:


Home page
RNAHome page
C. J. McManus, M. L. Schwartz, S. E. Butcher, and D. A. Brow
A dynamic bulge in the U6 RNA internal stem loop functions in spliceosome assembly and activation
RNA, December 1, 2007; 13(12): 2252 - 2265.
[Abstract] [Full Text] [PDF]


Home page
RNAHome page
S. Liu, R. Rauhut, H.-P. Vornlocher, and R. Luhrmann
The network of protein-protein interactions within the human U4/U6.U5 tri-snRNP
RNA, July 1, 2006; 12(7): 1418 - 1430.
[Abstract] [Full Text] [PDF]


Home page
RNAHome page
T. J. Brenner and C. Guthrie
Assembly of Snu114 into U5 snRNP requires Prp8 and a functional GTPase domain
RNA, May 1, 2006; 12(5): 862 - 871.
[Abstract] [Full Text] [PDF]


Home page
RNAHome page
P. BELLARE, A. K. KUTACH, A. K. RINES, C. GUTHRIE, and E. J. SONTHEIMER
Ubiquitin binding by a variant Jab1/MPN domain in the essential pre-mRNA splicing factor Prp8p
RNA, February 1, 2006; 12(2): 292 - 302.
[Abstract] [Full Text] [PDF]