Polypyrimidine tract binding protein controls the transition from exon definition to an intron defined spliceosome.
The polypyrimidine tract binding protein (PTB) binds pre-mRNAs to alter splice-site choice. We characterized a series of spliceosomal complexes that assemble on a pre-mRNA under conditions of either PTB-mediated splicing repression or its absence. In the absence of repression, exon definition complexes that were assembled downstream of the regulated exon could progress to pre-spliceosomal A complexes and functional spliceosomes. Under PTB-mediated repression, assembly was arrested at an A-like complex that was unable to transition to spliceosomal complexes. Trans-splicing experiments indicated that, even when the U1 and U2 small nuclear ribonucleoprotein particles (snRNPs) are properly bound to the upstream and downstream exons, the presence of PTB prevents the interaction of the two exon complexes. Proteomic analyses of these complexes provide a new description of exon definition complexes, and indicate that splicing regulators can act on the transition between the exon definition complex and an intron-defined spliceosome.
Sharma
Shalini
S
Howard Hughes Medical Institute, University of California, Los Angeles, MRL5-748, Charles E. Young Drive South, Los Angeles, California 90095, USA.
Kohlstaedt
Lori A
LA
Damianov
Andrey
A
Rio
Donald C
DC
Black
Douglas L
DL
D002457:Cell Extracts; D002460:Cell Line; D005091:Exons; D006801:Humans; D007438:Introns; D008954:Models, Biological; D038941:Polypyrimidine Tract-Binding Protein / Q000502:physiology*; D011485:Protein Binding; D011506:Proteins / Q000032:analysis; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000378:metabolism; D017381:Spliceosomes / Q000737:chemistry* / Q000378:metabolism*
D002457:Cell Extracts; D011506:Proteins; D012322:RNA Precursors; D017412:Ribonucleoprotein, U1 Small Nuclear; D017413:Ribonucleoprotein, U2 Small Nuclear; D038941:Polypyrimidine Tract-Binding Protein