Wh. Mcdonald et al., Myb-related fission yeast cdc5p is a component of a 40S snRNP-containing complex and is essential for pre-mRNA splicing, MOL CELL B, 19(8), 1999, pp. 5352-5362
Myb-related cdc5p is required for G(2)/M progression in the yeast Schizosac
charomyces pombe. We report here that all detectable cdc5p is stably associ
ated with a multiprotein 40S complex. Immunoaffinity purification has allow
ed the identification of 10 cwf (complexed with cdc5p) proteins. Two (cwf6p
and cwf10p) are members of the U5 snRNP; one (cwf9p) is a core snRNP prote
in. cwf8p is the apparent ortholog of the Saccharomyces cerevisiae splicing
factor Prp19p. cwf1(+) is allelic to the prp5(+) gene defined by the S. po
mbe splicing mutant, prp5-1, and there is a strong negative genetic interac
tion between cdc5-120 and prp5-1. Five cwfs have not been recognized previo
usly as important for either pre-mRNA splicing or cell cycle control. Furth
er characterization of cwf1p, cwf2p, cwf3p, and cwf4p demonstrates that the
y are encoded by essential genes, cosediment with cdc5p at 40S, and coimmun
oprecipitate with cdc5p, We further show that cdc5p associates with the U2,
U5, and U6 snRNAs and that cells lacking cdc5(+) function are defective in
pre-mRNA splicing. These data raise the possibility that the cdc5p complex
is an intermediate in the assembly or disassembly of an active S. pombe sp
liceosome.