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4pkd

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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Human spliceosomal U1 small nuclear ribonucleoprotein particles (snRNPs), which consist of U1 small nuclear RNA and ten proteins, recognize the 5' splice site within precursor messenger RNAs and initiate the assembly of the spliceosome for intron excision. An electron density map of the functional core of U1 snRNP at 5.5 A resolution has enabled us to build the RNA and, in conjunction with site-specific labelling of individual proteins, to place the seven Sm proteins, U1-C and U1-70K into the map. Here we present the detailed structure of a spliceosomal snRNP, revealing a hierarchical network of intricate interactions between subunits. A striking feature is the amino (N)-terminal polypeptide of U1-70K, which extends over a distance of 180 A from its RNA binding domain, wraps around the core domain consisting of the seven Sm proteins and finally contacts U1-C, which is crucial for 5'-splice-site recognition. The structure of U1 snRNP provides insights into U1 snRNP assembly and suggests a possible mechanism of 5'-splice-site recognition.
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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.
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Crystal structure of human spliceosomal U1 snRNP at 5.5 A resolution.,Pomeranz Krummel DA, Oubridge C, Leung AK, Li J, Nagai K Nature. 2009 Mar 26;458(7237):475-80. PMID:19325628<ref>PMID:19325628</ref>
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Crystal structure of human U1 snRNP, a small nuclear ribonucleoprotein particle, reveals the mechanism of 5' splice site recognition.,Kondo Y, Oubridge C, van Roon AM, Nagai K Elife. 2015 Jan 2;4. doi: 10.7554/eLife.04986. PMID:25555158<ref>PMID:25555158</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 07:46, 14 January 2015

U1-70k in complex with U1 snRNA stem-loops 1 and U1-A RRM in complex with stem-loop 2

4pkd, resolution 2.50Å

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