4m78
Crystal structure of Lsm2-8 complex, space group P21
Structural highlights
FunctionLSM6_YEAST Component of LSm protein complexes, which are involved in RNA processing and may function in a chaperone-like manner, facilitating the efficient association of RNA processing factors with their substrates. Component of the cytoplasmic LSM1-LSM7 complex, which is thought to be involved in mRNA degradation by activating the decapping step in the 5'-to-3' mRNA decay pathway. In association with PAT1, LSM1-LSM7 binds directly to RNAs near the 3'-end and prefers oligoadenylated RNAs over polyadenylated RNAs. Component of the nuclear LSM2-LSM8 complex, which is involved in splicing of nuclear mRNAs. LSM2-LSM8 associates with multiple snRNP complexes containing the U6 snRNA (U4/U6 di-snRNP, spliceosomal U4/U6.U5 tri-snRNP, and free U6 snRNP). It binds directly to the 3'-terminal U-tract of U6 snRNA and plays a role in the biogenesis and stability of the U6 snRNP and U4/U6 snRNP complexes. LSM2-LSM8 probably also is involved degradation of nuclear pre-mRNA by targeting them for decapping, and in processing of pre-tRNAs, pre-rRNAs and U3 snoRNA. Component of a nucleolar LSM2-LSM7 complex, which associates with the precursor of the RNA component of RNase P (pre-P RNA) and with the small nucleolar RNA (snoRNA) snR5. It may play a role in the maturation of a subset of nucleolus-associated small RNAs.[1] [2] [3] [4] Publication Abstract from PubMedSplicing of precursor messenger RNA (pre-mRNA) in eukaryotic cells is carried out by the spliceosome, which consists of five small nuclear ribonucleoproteins (snRNPs) and a number of accessory factors and enzymes. Each snRNP contains a ring-shaped subcomplex of seven proteins and a specific RNA molecule. The U6 snRNP contains a unique heptameric Lsm protein complex, which specifically recognizes the U6 small nuclear RNA at its 3' end. Here we report the crystal structures of the heptameric Lsm complex, both by itself and in complex with a 3' fragment of U6 snRNA, at 2.8 A resolution. Each of the seven Lsm proteins interacts with two neighbouring Lsm components to form a doughnut-shaped assembly, with the order Lsm3-2-8-4-7-5-6. The four uridine nucleotides at the 3' end of U6 snRNA are modularly recognized by Lsm3, Lsm2, Lsm8 and Lsm4, with the uracil base specificity conferred by a highly conserved asparagine residue. The uracil base at the extreme 3' end is sandwiched by His 36 and Arg 69 from Lsm3, through pi-pi and cation-pi interactions, respectively. The distinctive end-recognition of U6 snRNA by the Lsm complex contrasts with RNA binding by the Sm complex in the other snRNPs. The structural features and associated biochemical analyses deepen mechanistic understanding of the U6 snRNP function in pre-mRNA splicing. Crystal structures of the Lsm complex bound to the 3' end sequence of U6 small nuclear RNA.,Zhou L, Hang J, Zhou Y, Wan R, Lu G, Yin P, Yan C, Shi Y Nature. 2013 Nov 17. doi: 10.1038/nature12803. PMID:24240276[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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