Proteomic analysis of SRm160-containing complexes reveals a conserved association with cohesin.
In this study, we describe a rapid immunoaffinity purification procedure for gel-free tandem mass spectrometry-based analysis of endogenous protein complexes and apply it to the characterization of complexes containing the SRm160 (serine/arginine repeat-related nuclear matrix protein of 160 kDa) splicing coactivator. In addition to promoting splicing, SRm160 stimulates 3'-end processing via its N-terminal PWI nucleic acid-binding domain and is found in a post-splicing exon junction complex that has been implicated in coupling splicing with mRNA turnover, export, and translation. Consistent with these known functional associations, we found that the majority of proteins identified in SRm160-containing complexes are associated with pre-mRNA processing. Interestingly, SRm160 is also associated with factors involved in chromatin regulation and sister chromatid cohesion, specifically the cohesin subunits SMC1alpha, SMC3, RAD21, and SA2. Gradient fractionation suggested that there are two predominant SRm160-containing complexes, one enriched in splicing components and the other enriched in cohesin subunits. Co-immunoprecipitation and co-localization experiments, as well as combinatorial RNA interference in Caenorhabditis elegans, support the existence of conserved and functional interactions between SRm160 and cohesin.
McCracken
Susan
S
Banting and Best Department of Medical Research, C. H. Best Institute, Toronto, Ontario, Canada.
Longman
Dasa
D
Marcon
Edyta
E
Moens
Peter
P
Downey
Michael
M
Nickerson
Jeffrey A
JA
Jessberger
Rolf
R
Wilde
Andrew
A
Caceres
Javier F
JF
Emili
Andrew
A
Blencowe
Benjamin J
BJ
D000818:Animals; D034961:Antigens, Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017173:Caenorhabditis elegans / Q000235:genetics; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone; D005656:Fungal Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D034521:Nuclear Matrix-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D020543:Proteome; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000097722:Cohesins
D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D005656:Fungal Proteins; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D020543:Proteome; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000097722:Cohesins; C111710:SRRM1 protein, human