A polymorphic GT repeat from the human cardiac Na+Ca2+ exchanger intron 2 activates splicing

Eur J Biochem. 2001 Feb;268(4):1076-83. doi: 10.1046/j.1432-1327.2001.01974.x.


The sequence analysis of the human intron 2 from the Na+/Ca2+ exchanger 1 (NCX1) gene has revealed a GT repeat of variable length (10-16). The 5' sequence of intron 2 exhibited significant homology (65-70%) with other minisatellite sequences. DNA segments at the 5' end of intron 2 were inserted in the NCX1 cDNA (3.7 kb) to reconstruct the exon 2/intron 2 junction. Transient expression of these constructs in HEK293 cells generated shortened mRNAs ( approximately 2.5 kb). RT-PCR and ribonuclease protection analysis of the 3' end of the short transcripts indicated a splicing event at the intron 2/exon 2 junction (5' site) and in the vector sequence downstream of the NCX1 insert (3' site). Molecular dissection of the 5'-intron 2 sequence showed that the GT repeat was required for splicing activation, whereas the remainder of the 5'-intron 2 segment was completely inactive. The results indicate that the GT repeat is a strong intronic splicing enhancer that could be involved in the regulation of NCX1 expression, possibly mediating tissue-specific alternative splicing of the mutually exclusive exons 3 and 4, and/or exon-2 circularization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing
  • Base Sequence
  • Cell Line
  • Dinucleotide Repeats*
  • Humans
  • Introns
  • Molecular Sequence Data
  • Myocardium / metabolism*
  • Polymorphism, Genetic*
  • RNA Splice Sites
  • Ribonucleases / chemistry
  • Sequence Homology, Nucleic Acid
  • Sodium-Calcium Exchanger / genetics*
  • Sodium-Calcium Exchanger / metabolism
  • Transfection


  • RNA Splice Sites
  • Sodium-Calcium Exchanger
  • sodium-calcium exchanger 1
  • Ribonucleases