CIR, a corepressor of CBF1, binds to PAP-1 and effects alternative splicing

Exp Cell Res. 2005 Feb 15;303(2):375-87. doi: 10.1016/j.yexcr.2004.10.012. Epub 2004 Nov 18.


We have reported that PAP-1, a product of a causative gene for autosomal retinitis pigmentosa, plays a role in splicing. In this study, CIR, a protein originally identified as a CBF1-interacting protein and reported to act as a transcriptional corepressor, was identified as a PAP-1 binding protein and its function as a splicing factor was investigated. In addition to a basic lysine and acidic serine-rich (BA) domain and a zinc knuckle-like motif, CIR has an arginine/serine dipeptide repeat (RS) domain in its C terminal region. The RS domain has been reported to be present in the superfamily of SR proteins, which are involved in splicing reactions. We generated CIR mutants with deletions of each BA and RS domain and studied their subcellular localizations and interactions with PAP-1 and other SR proteins, including SC35, SF2/ASF, and U2AF35. CIR was found to interact with U2AF35 through the BA domain, with SC35 and SF2/ASF through the RS domain, and with PAP-1 outside the BA domain in vivo and in vitro. CIR was found to be colocalized with SC35 and PAP-1 in nuclear speckles. Then the effect of CIR on splicing was investigated using the E1a minigene as a reporter in HeLa cells. Ectopic expression of CIR with the E1a minigene changed the ratio of spliced isoforms of E1a that were produced by alternative selection of 5'-splice sites. These results indicate that CIR is a member of the family of SR-related proteins and that CIR plays a role in splicing regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing*
  • Amino Acid Sequence
  • Carrier Proteins / metabolism*
  • Cell Cycle Proteins
  • Cell Line
  • Cell Nucleus / metabolism
  • DNA-Binding Proteins / metabolism*
  • Genes, Reporter
  • HeLa Cells
  • Humans
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein
  • In Vitro Techniques
  • Molecular Sequence Data
  • Multiprotein Complexes
  • Nuclear Proteins / metabolism*
  • Pancreatitis-Associated Proteins
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Repressor Proteins / chemistry
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Sequence Deletion
  • Sequence Homology, Amino Acid
  • Two-Hybrid System Techniques


  • CIR1 protein, human
  • Carrier Proteins
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • INO80B protein, human
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein
  • Multiprotein Complexes
  • Nuclear Proteins
  • Pancreatitis-Associated Proteins
  • RBPJ protein, human
  • REG3A protein, human
  • Recombinant Proteins
  • Repressor Proteins