A polymorphic GT repeat from the human cardiac Na+Ca2+ exchanger intron 2 activates splicing.
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.
Gabellini
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Department of Biological Chemistry, University of Padova, Italy. nadiagab@civ.bio.unipd.it
D017398:Alternative Splicing; D001483:Base Sequence; D002460:Cell Line; D018900:Dinucleotide Repeats; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D011110:Polymorphism, Genetic; D022821:RNA Splice Sites; D012260:Ribonucleases / Q000737:chemistry; D012689:Sequence Homology, Nucleic Acid; D019831:Sodium-Calcium Exchanger / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
D022821:RNA Splice Sites; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D012260:Ribonucleases