Human PRP4 kinase is required for stable tri-snRNP association during spliceosomal B complex formation.
Reversible protein phosphorylation has an essential role during pre-mRNA splicing. Here we identify two previously unidentified phosphoproteins in the human spliceosomal B complex, namely the pre-mRNA processing factors PRP6 and PRP31, both components of the U4/U6-U5 tri-small nuclear ribonucleoprotein (snRNP). We provide evidence that PRP6 and PRP31 are directly phosphorylated by human PRP4 kinase (PRP4K) concomitant with their incorporation into B complexes. Immunodepletion and complementation studies with HeLa splicing extracts revealed that active human PRP4K is required for the phosphorylation of PRP6 and PRP31 and for the assembly of stable, functional B complexes. Thus, the phosphorylation of PRP6 and PRP31 is likely to have a key role during spliceosome assembly. Our data provide new insights into the molecular mechanism by which PRP4K contributes to splicing. They further indicate that numerous phosphorylation events contribute to spliceosome assembly and, thus, that splicing can potentially be modulated at multiple regulatory checkpoints.
Schneider
Marc
M
Department of Cellular Biochemistry, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.
Hsiao
He-Hsuan
HH
Will
Cindy L
CL
Giet
Régis
R
Urlaub
Henning
H
Lührmann
Reinhard
R
D005136:Eye Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D010766:Phosphorylation; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000378:metabolism*; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*; D017381:Spliceosomes / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
D005136:Eye Proteins; C454222:PRPF31 protein, human; C408605:PRPF6 protein, human; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; D014157:Transcription Factors; C489984:PRPF4B protein, human; D017346:Protein Serine-Threonine Kinases