title: Crystal structure of human U1 snRNP, a small nuclear ribonucleoprotein particle, reveals the mechanism of 5' splice site recognition.
abstract: U1 snRNP binds to the 5' exon-intron junction of pre-mRNA and thus plays a crucial role at an early stage of pre-mRNA splicing. We present two crystal structures of engineered U1 sub-structures, which together reveal at atomic resolution an almost complete network of protein-protein and RNA-protein interactions within U1 snRNP, and show how the 5' splice site of pre-mRNA is recognised by U1 snRNP. The zinc-finger of U1-C interacts with the duplex between pre-mRNA and the 5'-end of U1 snRNA. The binding of the RNA duplex is stabilized by hydrogen bonds and electrostatic interactions between U1-C and the RNA backbone around the splice junction but U1-C makes no base-specific contacts with pre-mRNA. The structure, together with RNA binding assays, shows that the selection of 5'-splice site nucleotides by U1 snRNP is achieved predominantly through basepairing with U1 snRNA whilst U1-C fine-tunes relative affinities of mismatched 5'-splice sites.
authors.affiliation: Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kondo
authors.affiliation: Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Oubridge
authors.affiliation: Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
authors.forename: Anne-Marie M
authors.initials: AM
authors.lastname: van Roon
authors.affiliation: Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nagai
mesh_terms: D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D022821:RNA Splice Sites; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D010455:Peptides; D022821:RNA Splice Sites; D012342:RNA, Small Nuclear; D017412:Ribonucleoprotein, U1 Small Nuclear; C405483:U1 small nuclear RNA
keywords: 5′ splice site; U1 snRNP; biophysics; crystallography; human; pre-mRNA splicing; spliceosome; structural biology