title: A spliceosomal intron binding protein, IBP160, links position-dependent assembly of intron-encoded box C/D snoRNP to pre-mRNA splicing.
abstract: Pre-mRNA splicing in vertebrates is molecularly linked to other processes. We previously reported that splicing is required for efficient assembly of intron-encoded box C/D small nucleolar ribonucleoprotein (snoRNP). In the spliceosomal C1 complex, snoRNP proteins efficiently assemble onto snoRNA sequences if they are located about 50 nt upstream of the intron branchpoint. Here, we identify the splicing factor responsible for coupling snoRNP assembly to intron excision. Intron binding protein (IBP) 160, a helicase-like protein previously detected in the spliceosomal C1 complex, binds the pre-mRNA in a sequence-independent manner, contacting nucleotides 33-40 upstream of the intron branch site, regardless of whether a snoRNA is present. Depletion of IBP160 abrogates snoRNP assembly in vitro. IBP160 binding directly to a snoRNA located too close to the intron branch site interferes with snoRNP assembly. Thus, IBP160 is the key factor linking snoRNP biogenesis and perhaps other postsplicing events to pre-mRNA splicing.
authors.affiliation: Biological Information Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, 135-0064, Japan. tehirose@jbirc.aist.go.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Hirose
authors.forename: Takashi
authors.initials: T
authors.lastname: Ideue
authors.forename: Misato
authors.initials: M
authors.lastname: Nagai
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Hagiwara
authors.forename: Mei-Di
authors.initials: MD
authors.lastname: Shu
authors.forename: Joan A
authors.initials: JA
authors.lastname: Steitz
mesh_terms: D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007438:Introns / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D020365:RNA Helicases / Q000378:metabolism; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing / Q000235:genetics*; D020537:RNA, Small Nucleolar / Q000737:chemistry / Q000235:genetics; D020718:Ribonucleoproteins, Small Nucleolar / Q000096:biosynthesis / Q000378:metabolism*; D017381:Spliceosomes / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D012322:RNA Precursors; D020537:RNA, Small Nucleolar; D020718:Ribonucleoproteins, Small Nucleolar; D020365:RNA Helicases