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Gene Review

SNRPA  -  small nuclear ribonucleoprotein polypeptide A

Homo sapiens

Synonyms: Mud1, U1 small nuclear ribonucleoprotein A, U1 snRNP A, U1-A, U1A
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Disease relevance of SNRPA

  • We demonstrate that the DExH protein NPH-II from vaccinia virus can displace the protein U1A from RNA in an active adenosine triphosphate-dependent fashion [1].
  • Experiments with a mixture of recombinant phage displaying U1A or the closely related protein U2B" demonstrated that addition of a competitor RNA can suppress selection of a protein with a higher affinity for a given RNA target, thereby allowing the preferential amplification of a lower affinity protein [2].
  • A subset of lupus patients with severe nephritis and anti-nRNP reactivity produces autoantibodies primarily against two major epitopes of the nRNP A (also known as U1A) protein [3].
  • The U1A domain responsible for binding to U1 small nuclear RNA was locally mutagenized and displayed as a combinatorial library on filamentous bacteriophage [4].
  • Using hairpin II of U1 small nuclear RNA (U1hpII) or the 3' stem loop of histone mRNA as bait, we could selectively amplify T7 phage that display either the spliceosomal protein U1A or the histone stem loop-binding protein from a lung cDNA phage library containing more than 10(7) independent clones [2].

High impact information on SNRPA


Biological context of SNRPA


Anatomical context of SNRPA


Associations of SNRPA with chemical compounds

  • Since helix C undergoes a conformational change upon RNA binding, the structure shows that binding cooperativity and interactions with PAP occur only when U1A is bound to its cognate RNA [8].
  • Adenosine triphosphate is capable of supporting U1A and U2B" import, whereas neither nonhydrolyzable adenosine triphosphate analogues nor GTP can do so [10].
  • 13C NMR relaxation studies of RNA base and ribose nuclei reveal a complex pattern of motions in the RNA binding site for human U1A protein [16].
  • However, the proline-rich region of U1-A, absent in U2-B", is encoded by a single exon, suggesting a specific function for this domain of U1-A [17].
  • In this study, autoantibody recognition of native U1 snRNPs was investigated by dissociating the particle into four components (U1-70K, U1-A, U1-C, and the Sm core particle) using 1 M MgCl2 or ribonuclease treatment [18].

Physical interactions of SNRPA

  • The NMR structure of the 38 kDa complex formed between two U1A molecules and PIE RNA shows that binding cooperativity depends on helix C located at the end of the RNA-binding domain and just adjacent to the PAP-interacting domain of U1A [8].
  • Here we examined the effect of randomizing amino acids in the heavy chain complementarity determining region 3 (CDR3) of this germline encoded recombinant antibody fragment on binding to the U1A protein [19].

Other interactions of SNRPA


Analytical, diagnostic and therapeutic context of SNRPA

  • Using both coselection and gel mobility shift assays, U1A dimerization was also observed in vitro and found to depend on the same two regions that were found in vivo [11].
  • Antibodies against U1A (tested in Western immunoblotting with HeLa cell extracts) were positively associated to DRB1*06 allele; antibodies reacting with SmD1 peptide 44-67 were negatively associated to DRB1*02 and DQB1*0602 alleles [20].
  • We have now used GST fusion protein experiments, coimmunoprecipitations and Far Western blot analyses to demonstrate direct binding between U1A and the 160-kD subunit of cleavage-polyadenylation specificity factor (CPSF) [21].
  • We report here that the rapidly formed intermediate of the spliceosomal protein U1A is an off-pathway artefact caused by transient aggregation of denatured protein under native conditions [22].
  • T cell epitope mapping of U1-A RNP [23].


  1. Active disruption of an RNA-protein interaction by a DExH/D RNA helicase. Jankowsky, E., Gross, C.H., Shuman, S., Pyle, A.M. Science (2001) [Pubmed]
  2. T7 phage display: a novel genetic selection system for cloning RNA-binding proteins from cDNA libraries. Danner, S., Belasco, J.G. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  3. Structural availability influences the capacity of autoantigenic epitopes to induce a widespread lupus-like autoimmune response. McClain, M.T., Lutz, C.S., Kaufman, K.M., Faig, O.Z., Gross, T.F., James, J.A. Proc. Natl. Acad. Sci. U.S.A. (2004) [Pubmed]
  4. Analysis of RNA-binding proteins by in vitro genetic selection: identification of an amino acid residue important for locking U1A onto its RNA target. Laird-Offringa, I.A., Belasco, J.G. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  5. The human U1A snRNP protein regulates polyadenylation via a direct interaction with poly(A) polymerase. Gunderson, S.I., Beyer, K., Martin, G., Keller, W., Boelens, W.C., Mattaj, L.W. Cell (1994) [Pubmed]
  6. The human U1 snRNP-specific U1A protein inhibits polyadenylation of its own pre-mRNA. Boelens, W.C., Jansen, E.J., van Venrooij, W.J., Stripecke, R., Mattaj, I.W., Gunderson, S.I. Cell (1993) [Pubmed]
  7. Crystal structure of the spliceosomal U2B"-U2A' protein complex bound to a fragment of U2 small nuclear RNA. Price, S.R., Evans, P.R., Nagai, K. Nature (1998) [Pubmed]
  8. The NMR structure of the 38 kDa U1A protein - PIE RNA complex reveals the basis of cooperativity in regulation of polyadenylation by human U1A protein. Varani, L., Gunderson, S.I., Mattaj, I.W., Kay, L.E., Neuhaus, D., Varani, G. Nat. Struct. Biol. (2000) [Pubmed]
  9. Crystal structure of the RNA-binding domain of the U1 small nuclear ribonucleoprotein A. Nagai, K., Oubridge, C., Jessen, T.H., Li, J., Evans, P.R. Nature (1990) [Pubmed]
  10. An ATP-dependent, Ran-independent mechanism for nuclear import of the U1A and U2B" spliceosome proteins. Hetzer, M., Mattaj, I.W. J. Cell Biol. (2000) [Pubmed]
  11. Fourteen residues of the U1 snRNP-specific U1A protein are required for homodimerization, cooperative RNA binding, and inhibition of polyadenylation. Klein Gunnewiek, J.M., Hussein, R.I., van Aarssen, Y., Palacios, D., de Jong, R., van Venrooij, W.J., Gunderson, S.I. Mol. Cell. Biol. (2000) [Pubmed]
  12. p54nrb is a component of the snRNP-free U1A (SF-A) complex that promotes pre-mRNA cleavage during polyadenylation. Liang, S., Lutz, C.S. RNA (2006) [Pubmed]
  13. Clonotype analysis of peripheral blood T cells and autoantigen-reactive T cells from patients with mixed connective tissue disease. Okubo, M., Kurokawa, M., Ohto, H., Nishimaki, T., Nishioka, K., Kasukawa, R., Yamamoto, K. J. Immunol. (1994) [Pubmed]
  14. Altered expression level of a systemic nuclear autoantigen determines the fate of immune response to self. Kawahata, K., Misaki, Y., Komagata, Y., Setoguchi, K., Tsunekawa, S., Yoshikawa, Y., Miyazaki, J., Yamamoto, K. J. Immunol. (1999) [Pubmed]
  15. Bacteriophage and spliceosomal proteins function as position-dependent cis/trans repressors of mRNA translation in vitro. Stripecke, R., Hentze, M.W. Nucleic Acids Res. (1992) [Pubmed]
  16. 13C NMR relaxation studies of RNA base and ribose nuclei reveal a complex pattern of motions in the RNA binding site for human U1A protein. Shajani, Z., Varani, G. J. Mol. Biol. (2005) [Pubmed]
  17. Structure, chromosomal localization and evolutionary conservation of the gene encoding human U1 snRNP-specific A protein. Nelissen, R.L., Sillekens, P.T., Beijer, R.P., Geurts van Kessel, A.H., van Venrooij, W.J. Gene (1991) [Pubmed]
  18. Human anti-nuclear ribonucleoprotein antigen autoimmune sera contain a novel subset of autoantibodies that stabilizes the molecular interaction of U1RNP-C protein with the Sm core proteins. Satoh, M., Richards, H.B., Hamilton, K.J., Reeves, W.H. J. Immunol. (1997) [Pubmed]
  19. Heavy chain CDR3 optimization of a germline encoded recombinant antibody fragment predisposed to bind the U1A protein. de Wildt, R.M., Ruytenbeek, R., van Venrooij, W.J., Hoet, R.M. Protein Eng. (1997) [Pubmed]
  20. MHC class II gene associations with autoantibodies to U1A and SmD1 proteins. Dumortier, H., Abbal, M., Fort, M., Briand, J.P., Cantagrel, A., Muller, S. Int. Immunol. (1999) [Pubmed]
  21. Interaction between the U1 snRNP-A protein and the 160-kD subunit of cleavage-polyadenylation specificity factor increases polyadenylation efficiency in vitro. Lutz, C.S., Murthy, K.G., Schek, N., O'Connor, J.P., Manley, J.L., Alwine, J.C. Genes Dev. (1996) [Pubmed]
  22. Transient aggregates in protein folding are easily mistaken for folding intermediates. Silow, M., Oliveberg, M. Proc. Natl. Acad. Sci. U.S.A. (1997) [Pubmed]
  23. T cell epitope mapping of U1-A RNP. Okubo, M., Kokubun, M., Nishimaki, T., Kasukawa, R., Ohto, H., Yamamoto, K., Muller, S. Arthritis Rheum. (1995) [Pubmed]
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