U11/U12-65K is a spliceosomal protein encoded by the RNPC3 gene in humans. It is a component of the U11/U12 di-snRNP and one of the proteins found in the U12-dependent spliceosome, but not in the U2-dependent spliceosome.
Introduction
Most eukaryotic genomes harbor two types of spliceosomal introns, called U2-type and U12-type introns, which are excised by two different spliceosomes. U12-type introns are rare, and only present a small fraction of introns in any given eukaryotic genome. The U12-dependent spliceosome, also called the minor spliceosome, is responsible for the removal of these rare introns. Both spliceosomes consist of five small nuclear ribonucleoprotein particles (snRNPs), which are U1, U2, U4, U5 and U6 for the U2-dependent spliceosome and U11, U12, U4atac, U5 and U6atac for the U12-dependent spliceosome. The protein composition of the two spliceosomes is similar, and so far only seven proteins specific for the minor spliceosome have been identified[1][2][3]. All seven proteins (called 65K, 59K, 48K, 35K, 31K, 25K and 20K) are components of the U11/U12 di-snRNP[3] that is responsible for the initial recognition of the U12-type splice sites and bridging of the 5' and 3' ends of the intron.
The U11/U12-65K protein forms part of a molecular bridge that connects the U11 and U12 snRNPs[4], and is important for the stability of the U11/U12 di-snRNP and splicing of U12-type introns[5][6][7]. It binds to U12 snRNA and U11-59K[4][8], a protein component of the U11 snRNP.
Structure
Domain structure
The human U11/U12-65K protein contains two RNA recognition motifs (RRM), one close to the N-terminus (residues 27-102) and another one near the C-terminus (residues 420–503), as well as a proline-rich region (residues 196–233) located between the two RRMs. The C-terminal RRM exhibits higher conservation, and is likely homologous to the N-terminal RRMs of the U1-A and U2-B" proteins[4], which are components of the U1 and U2 snRNPs, respectively. The C-terminal RRM binds specifically to stem-loop III of U12 snRNA, whereas the N-terminal half of the protein (residues 1–257), which includes the second RRM and the proline-rich region, interacts with the U11-59K protein[4].
Crystal structure of human U11/U12-65K
The structure of the C-terminal RNA recognition motif and an associated N-terminal extension of human U11/U12-65K has been determined by X-ray crystallography at 2.5 Å resolution[9]. Residues 417–501 adopt a typical RRM fold, with an antiparallel four-stranded β-sheet packed against two α-helices. In addition to these canonical elements, the 65K C-terminal RRM contains a short helix between the α1 helix and the β2 strand.
Disease association
Mutations in the gene encoding the U11/U12-65K protein (RNPC3) were recently shown to cause isolated growth hormone deficiency (IGHD) and pituitary hypoplasia[5].
References
- ↑ Will CL, Schneider C, Reed R, Luhrmann R. Identification of both shared and distinct proteins in the major and minor spliceosomes. Science. 1999 Jun 18;284(5422):2003-5. PMID:10373121
- ↑ Schneider C, Will CL, Makarova OV, Makarov EM, Luhrmann R. Human U4/U6.U5 and U4atac/U6atac.U5 tri-snRNPs exhibit similar protein compositions. Mol Cell Biol. 2002 May;22(10):3219-29. PMID:11971955
- ↑ 3.0 3.1 Will CL, Schneider C, Hossbach M, Urlaub H, Rauhut R, Elbashir S, Tuschl T, Luhrmann R. The human 18S U11/U12 snRNP contains a set of novel proteins not found in the U2-dependent spliceosome. RNA. 2004 Jun;10(6):929-41. PMID:15146077
- ↑ 4.0 4.1 4.2 4.3 Benecke H, Luhrmann R, Will CL. The U11/U12 snRNP 65K protein acts as a molecular bridge, binding the U12 snRNA and U11-59K protein. EMBO J. 2005 Sep 7;24(17):3057-69. Epub 2005 Aug 11. PMID:16096647 doi:http://dx.doi.org/7600765
- ↑ 5.0 5.1 Argente J, Flores R, Gutierrez-Arumi A, Verma B, Martos-Moreno GA, Cusco I, Oghabian A, Chowen JA, Frilander MJ, Perez-Jurado LA. Defective minor spliceosome mRNA processing results in isolated familial growth hormone deficiency. EMBO Mol Med. 2014 Mar;6(3):299-306. doi: 10.1002/emmm.201303573. Epub 2014 Jan, 30. PMID:24480542 doi:http://dx.doi.org/10.1002/emmm.201303573
- ↑ Markmiller S, Cloonan N, Lardelli RM, Doggett K, Keightley MC, Boglev Y, Trotter AJ, Ng AY, Wilkins SJ, Verkade H, Ober EA, Field HA, Grimmond SM, Lieschke GJ, Stainier DY, Heath JK. Minor class splicing shapes the zebrafish transcriptome during development. Proc Natl Acad Sci U S A. 2014 Feb 25;111(8):3062-7. doi:, 10.1073/pnas.1305536111. Epub 2014 Feb 10. PMID:24516132 doi:http://dx.doi.org/10.1073/pnas.1305536111
- ↑ Jung HJ, Kang H. The Arabidopsis U11/U12-65K is an indispensible component of minor spliceosome and plays a crucial role in U12 intron splicing and plant development. Plant J. 2014 Mar 8. doi: 10.1111/tpj.12498. PMID:24606192 doi:http://dx.doi.org/10.1111/tpj.12498
- ↑ Turunen JJ, Will CL, Grote M, Luhrmann R, Frilander MJ. The U11-48K protein contacts the 5' splice site of U12-type introns and the U11-59K protein. Mol Cell Biol. 2008 May;28(10):3548-60. doi: 10.1128/MCB.01928-07. Epub 2008 Mar , 17. PMID:18347052 doi:http://dx.doi.org/10.1128/MCB.01928-07
- ↑ Netter C, Weber G, Benecke H, Wahl MC. Functional stabilization of an RNA recognition motif by a noncanonical N-terminal expansion. RNA. 2009 Jul;15(7):1305-13. Epub 2009 May 15. PMID:19447915 doi:10.1261/rna.1359909
