The Prp19 complex and the Usp4Sart3 deubiquitinating enzyme control reversible ubiquitination at the spliceosome.
The spliceosome, a dynamic assembly of proteins and RNAs, catalyzes the excision of intron sequences from nascent mRNAs. Recent work has suggested that the activity and composition of the spliceosome are regulated by ubiquitination, but the underlying mechanisms have not been elucidated. Here, we report that the spliceosomal Prp19 complex modifies Prp3, a component of the U4 snRNP, with nonproteolytic K63-linked ubiquitin chains. The K63-linked chains increase the affinity of Prp3 for the U5 snRNP component Prp8, thereby allowing for the stabilization of the U4/U6.U5 snRNP. Prp3 is deubiquitinated by Usp4 and its substrate targeting factor, the U4/U6 recycling protein Sart3, which likely facilitates ejection of U4 proteins from the spliceosome during maturation of its active site. Loss of Usp4 in cells interferes with the accumulation of correctly spliced mRNAs, including those for alpha-tubulin and Bub1, and impairs cell cycle progression. We propose that the reversible ubiquitination of spliceosomal proteins, such as Prp3, guides rearrangements in the composition of the spliceosome at distinct steps of the splicing reaction.
Song
Eun Joo
EJ
Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.
Werner
Shannon L
SL
Neubauer
Jakob
J
Stegmeier
Frank
F
Aspden
Julie
J
Rio
Donald
D
Harper
J Wade
JW
Elledge
Stephen J
SJ
Kirschner
Marc W
MW
Rape
Michael
M
D000951:Antigens, Neoplasm / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D019154:Protein Splicing / Q000502:physiology; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000378:metabolism*; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D043222:Ubiquitin Thiolesterase / Q000378:metabolism*; D064570:Ubiquitin-Specific Proteases; D054875:Ubiquitination
D000951:Antigens, Neoplasm; D009687:Nuclear Proteins; C108507:PRPF3 protein, human; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; C416530:SART3 protein, human; C486203:USP4 protein, human; D025801:Ubiquitin; D043222:Ubiquitin Thiolesterase; D064570:Ubiquitin-Specific Proteases; D045643:DNA Repair Enzymes; C417041:PRPF19 protein, human