| First Author | van Dijk MA | Year | 2001 |
| Journal | J Mol Evol | Volume | 52 |
| Issue | 6 | Pages | 510-5 |
| PubMed ID | 11443354 | Mgi Jnum | J:69817 |
| Mgi Id | MGI:2135504 | Doi | 10.1007/s002390010181 |
| Citation | van Dijk MA, et al. (2001) The Evolution of an Alternatively Spliced Exon in the alphaA-Crystallin Gene. J Mol Evol 52(6):510-5 |
| abstractText | The evolutionary aspects of alternative splicing, as a mechanism to increase the diversity of gene products, are poorly understood. Here we analyse the evolution of a 69-bp exon that is alternatively spliced in the primary transcript of the gene for the mammalian eye lens protein alphaA-crystallin. In rodents, the skipping of this exon 2 is attributed to the presence of a non-consensus 5' splice site GC, and results in the expression of 10-20% of alphaAins-crystallin, with an insert of 23 residues, as compared with normal alphaA-crystallin. alphaAins-crystallin is also expressed in some non-rodent mammals, including kangaroo, while lacking in others. We now demonstrate that the alternatively spliced exon 2 is present in mammals from different orders that do not express alphaAins-crystallin. The expression of this exon has thus been silenced independently in various lineages. Sequence comparison in 16 species reveals that-whether or not alphaAins-crystallin is expressed-exon 2 is always flanked by the non-consensus donor splice site GC, while a consensus branch point sequence and 3' pyrimidine-rich region are hardly detectable in the downstream intron. Increased numbers of amino acid replacements in the peptide encoded by exon 2 indicate that it is subject to much lower selective constraints than the exons that code for normal alphaA-crystallin. The absence of any apparent advantage at the protein level may suggest that exon 2 DNA sequences are conserved as cis-acting factors for proper splicing of the alphaA-crystallin transcript. |
