title: The SRm160/300 splicing coactivator subunits.
abstract: The SRm160/300 splicing coactivator, which consists of the serine/arginine (SR)-related nuclear matrix protein of 160 kDa and a 300-kDa nuclear matrix antigen, functions in splicing by promoting critical interactions between splicing factors bound to pre-mRNA, including snRNPs and SR family proteins. In this article we report the isolation of a cDNA encoding the 300-kDa antigen and investigate the activity of it and SRm160 in splicing. Like SRm160, the 300-kDa antigen contains domains rich in alternating S and R residues but lacks an RNA recognition motif; the protein is accordingly named "SRm300." SRm300 also contains a novel and highly conserved N-terminal domain, several unique repeated motifs rich in S, R, and proline residues, and two very long polyserine tracts. Surprisingly, specific depletion of SRm300 does not prevent the splicing of pre-mRNAs shown previously to require SRm160/300. Addition of recombinant SRm160 alone to SRm160/300-depleted reactions specifically activates splicing. The results indicate that SRm160 may be the more critical component of the SRm160/300 coactivator in the splicing of SRm160/300-dependent pre-mRNAs.
authors.affiliation: Center for Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Blencowe
authors.forename: G
authors.initials: G
authors.lastname: Baurén
authors.forename: A G
authors.initials: AG
authors.lastname: Eldridge
authors.forename: R
authors.initials: R
authors.lastname: Issner
authors.forename: J A
authors.initials: JA
authors.lastname: Nickerson
authors.forename: E
authors.initials: E
authors.lastname: Rosonina
authors.forename: P A
authors.initials: PA
authors.lastname: Sharp
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D034961:Antigens, Nuclear; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D011233:Precipitin Tests; D012326:RNA Splicing / Q000235:genetics* / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D017381:Spliceosomes / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D034961:Antigens, Nuclear; D018076:DNA, Complementary; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C111710:SRRM1 protein, human; C414618:SRRM2 protein, human