6ahd | pdb_00006ahd
The Cryo-EM Structure of Human Pre-catalytic Spliceosome (B complex) at 3.8 angstrom resolution
Structural highlights
Disease[U5S1_HUMAN] Mandibulofacial dysostosis-microcephaly syndrome. The disease is caused by mutations affecting the gene represented in this entry. [PRP8_HUMAN] Defects in PRPF8 are the cause of retinitis pigmentosa type 13 (RP13) [MIM:600059]. RP leads to degeneration of retinal photoreceptor cells. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well. RP13 inheritance is autosomal dominant.[1] [2] [:][3] [4] [U520_HUMAN] Retinitis pigmentosa. Retinitis pigmentosa 33 (RP33) [MIM:610359]: A retinal dystrophy belonging to the group of pigmentary retinopathies. Retinitis pigmentosa is characterized by retinal pigment deposits visible on fundus examination and primary loss of rod photoreceptor cells followed by secondary loss of cone photoreceptors. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well. Note=The disease is caused by mutations affecting the gene represented in this entry.[5] [6] [7] [8] [9] [PRP31_HUMAN] Defects in PRPF31 are the cause of retinitis pigmentosa type 11 (RP11) [MIM:600138]. RP leads to degeneration of retinal photoreceptor cells. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well. RP11 inheritance is autosomal dominant.[10] [11] [12] [13] [14] [SF3B4_HUMAN] Defects in SF3B4 are the cause of acrofacial dysostosis type 1 (AFD1) [MIM:154400]. AFD1 is a form of acrofacial dysostosis, a group of disorders which are characterized by malformation of the craniofacial skeleton and the limbs. The major facial features of AFD1 include downslanted palpebral fissures, midface retrusion, and micrognathia, the latter of which often requires the placement of a tracheostomy in early childhood. Limb defects typically involve the anterior (radial) elements of the upper limbs and manifest as small or absent thumbs, triphalangeal thumbs, radial hyoplasia or aplasia, and radioulnar synostosis. Phocomelia of the upper limbs and, occasionally, lower-limb defects have also been reported.[15] [PRPF3_HUMAN] Defects in PRPF3 are the cause of retinitis pigmentosa type 18 (RP18) [MIM:601414]. RP leads to degeneration of retinal photoreceptor cells. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well. RP18 inheritance is autosomal dominant.[16] [17] [18] [PRP6_HUMAN] Retinitis pigmentosa. The disease may be caused by mutations affecting the gene represented in this entry. Cells from RP60 patients show intron retention for pre-mRNA bearing specific splicing signals. Function[SF3A3_HUMAN] Subunit of the splicing factor SF3A required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. [SF3A2_HUMAN] Subunit of the splicing factor SF3A required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. [WBP4_HUMAN] Promotes pre-mRNA splicing. A spliceosome-associated protein; may play a role in cross-intron bridging of U1 and U2 snRNPs in the mammalian A complex.[19] [20] [U5S1_HUMAN] Component of the U5 snRNP and the U4/U6-U5 tri-snRNP complex required for pre-mRNA splicing. Binds GTP. [PRP8_HUMAN] Central component of the spliceosome, which may play a role in aligning the pre-mRNA 5'- and 3'-exons for ligation. Interacts with U5 snRNA, and with pre-mRNA 5'-splice sites in B spliceosomes and 3'-splice sites in C spliceosomes. [RUXG_HUMAN] Appears to function in the U7 snRNP complex that is involved in histone 3'-end processing. Associated with snRNP U1, U2, U4/U6 and U5. [RU2B_HUMAN] Involved in pre-mRNA splicing. This protein is associated with snRNP U2. It binds stem loop IV of U2 snRNA only in presence of the U2A' protein. [SF3B6_HUMAN] Involved in pre-mRNA splicing as a component of the splicing factor SF3B complex (PubMed:27720643). SF3B complex is required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA (PubMed:12234937). Directly contacts the pre-mRNA branch site adenosine for the first catalytic step of splicing (PubMed:16432215). Enters the spliceosome and associates with the pre-mRNA branch site as part of the 17S U2 or, in the case of the minor spliceosome, as part of the 18S U11/U12 snRNP complex, and thus may facilitate the interaction of these snRNP with the branch sites of U2 and U12 respectively (PubMed:16432215).[21] [22] [23] [PR38A_HUMAN] May be required for pre-mRNA splicing. [LSM8_HUMAN] Binds specifically to the 3'-terminal U-tract of U6 snRNA and is probably a component of the spliceosome. [SNR40_HUMAN] Component of the U5 small nuclear ribonucleoprotein (snRNP) complex. The U5 snRNP is part of the spliceosome, a multiprotein complex that catalyzes the removal of introns from pre-messenger RNAs.[24] [SMD1_HUMAN] May act as a charged protein scaffold to promote snRNP assembly or strengthen snRNP-snRNP interactions through nonspecific electrostatic contacts with RNA. [U520_HUMAN] RNA helicase that plays an essential role in pre-mRNA splicing as component of the U5 snRNP and U4/U6-U5 tri-snRNP complexes. Involved in spliceosome assembly, activation and disassembly. Mediates changes in the dynamic network of RNA-RNA interactions in the spliceosome. Catalyzes the ATP-dependent unwinding of U4/U6 RNA duplices, an essential step in the assembly of a catalytically active spliceosome.[25] [26] [27] [28] [MFAP1_HUMAN] Component of the elastin-associated microfibrils. [PRP31_HUMAN] Involved in pre-mRNA splicing. Required for U4/U6.U5 tri-snRNP formation.[29] [SF3A1_HUMAN] Subunit of the splicing factor SF3A required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. [LSM3_HUMAN] Binds specifically to the 3'-terminal U-tract of U6 snRNA. [SNUT1_HUMAN] Plays a role in mRNA splicing as a component of the U4/U6-U5 tri-snRNP, one of the building blocks of the spliceosome. May also bind to DNA.[30] [SF3B4_HUMAN] Subunit of the splicing factor SF3B required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. SF3B4 has been found in complex 'B' and 'C' as well. Belongs also to the minor U12-dependent spliceosome, which is involved in the splicing of rare class of nuclear pre-mRNA intron. [SF3B1_HUMAN] Subunit of the splicing factor SF3B required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. Belongs also to the minor U12-dependent spliceosome, which is involved in the splicing of rare class of nuclear pre-mRNA intron. [PPIH_HUMAN] PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Participates in pre-mRNA splicing. May play a role in the assembly of the U4/U5/U6 tri-snRNP complex. May act as a chaperone.[31] [32] [33] [RU2A_HUMAN] This protein is associated with sn-RNP U2. It helps the A' protein to bind stem loop IV of U2 snRNA. [TXN4A_HUMAN] Essential role in pre-mRNA splicing. [LSM7_HUMAN] Binds specifically to the 3'-terminal U-tract of U6 snRNA and is probably a component of the spliceosome. [LSM4_HUMAN] Binds specifically to the 3'-terminal U-tract of U6 snRNA. [NH2L1_HUMAN] Binds to the 5'-stem-loop of U4 snRNA and may play a role in the late stage of spliceosome assembly. The protein undergoes a conformational change upon RNA-binding.[34] [35] [PRP4_HUMAN] Involved in pre-mRNA splicing. [PRPF3_HUMAN] Participates in pre-mRNA splicing. May play a role in the assembly of the U4/U5/U6 tri-snRNP complex. [SF3B2_HUMAN] Subunit of the splicing factor SF3B required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. Belongs also to the minor U12-dependent spliceosome, which is involved in the splicing of rare class of nuclear pre-mRNA intron. [SMD2_HUMAN] Required for pre-mRNA splicing. Required for snRNP biogenesis (By similarity). [LSM6_HUMAN] 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. 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 (By similarity). [PRP6_HUMAN] Involved in pre-mRNA splicing as component of the U4/U6-U5 tri-snRNP complex, one of the building blocks of the spliceosome. Enhances dihydrotestosterone-induced transactivation activity of AR, as well as dexamethasone-induced transactivation activity of NR3C1, but does not affect estrogen-induced transactivation.[36] [LSM2_HUMAN] Binds specifically to the 3'-terminal U-tract of U6 snRNA. May be involved in pre-mRNA splicing. [PHF5A_HUMAN] Acts as a transcriptional regulator by binding to the GJA1/Cx43 promoter and enhancing its up-regulation by ESR1/ER-alpha. Also involved in pre-mRNA splicing.[37] [LSM5_HUMAN] Plays a role in U6 snRNP assembly and function. Binds to the 3' end of U6 snRNA, thereby facilitating formation of the spliceosomal U4/U6 duplex formation in vitro. [SF3B3_HUMAN] Subunit of the splicing factor SF3B required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. Belongs also to the minor U12-dependent spliceosome, which is involved in the splicing of rare class of nuclear pre-mRNA intron. [SMD3_HUMAN] Appears to function in the U7 snRNP complex that is involved in histone 3'-end processing. Binds to the downstream cleavage product (DCP) of histone pre-mRNA in a U7 snRNP dependent manner.[38] Publication Abstract from PubMedThe pre-catalytic spliceosome (B complex) is preceded by its precursor spliceosome (pre-B complex) and followed by the activated spliceosome (B(act) complex). The pre-B-to-B and B-to-B(act) transitions are driven by the ATPase/helicases Prp28 and Brr2, respectively. In this study, we report the cryo-electron microscopy structures of the human pre-B complex and the human B complex at an average resolution of 5.7 and 3.8 A, respectively. In the pre-B complex, U1 and U2 small nuclear ribonucleoproteins (snRNPs) associate with two edges of the tetrahedron-shaped U4/U6.U5 tri-snRNP. The pre-mRNA is yet to be recognized by U5 or U6 small nuclear RNA (snRNA), and loop I of U5 snRNA remains unengaged. In the B complex, U1 snRNP and Prp28 are dissociated, the 5'-exon is anchored to loop I of U5 snRNA, and the 5'-splice site is recognized by U6 snRNA through duplex formation. In sharp contrast to S. cerevisiae, most components of U2 snRNP and tri-snRNP, exemplified by Brr2, undergo pronounced rearrangements in the human pre-B-to-B transition. Structural analysis reveals mechanistic insights into the assembly and activation of the human spliceosome. Structures of the human pre-catalytic spliceosome and its precursor spliceosome.,Zhan X, Yan C, Zhang X, Lei J, Shi Y Cell Res. 2018 Oct 12. pii: 10.1038/s41422-018-0094-7. doi:, 10.1038/s41422-018-0094-7. PMID:30315277[39] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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