Gally J A, Edelman G M
Neurosciences Institute of the Neurosciences Research Program, New York, NY.
Proc Natl Acad Sci U S A. 1992 Apr 15;89(8):3276-9. doi: 10.1073/pnas.89.8.3276.
The genomic sequences encoding a chicken Ca(2+)-dependent cell adhesion molecule (K-CAM) were recently found to be located approximately 600 base pairs upstream from the translation initiation site of a homologous protein, liver CAM. The sizes of 11 exons of the K-CAM gene are almost identical to those in the L-CAM (liver cell-adhesion molecule) gene with exon-intron junctions occurring at exactly equivalent positions. The sizes and sequences of most introns were, however, much more dissimilar. More detailed comparisons of these two genes reveal that the sequences of the last two exons (exons 15 and 16) are far more alike than are any of the other exons; they are, in fact, almost identical. The introns that separate these exons in the two genes likewise resemble one another far more than do any other corresponding introns. This degree of similarity appears to be far greater than can be accounted for by selection for protein structure, and it strongly suggests that a gene conversion event occurred between these two genes subsequent to their duplication and divergence to perform different biological functions.
最近发现，编码鸡钙依赖性细胞粘附分子（K-CAM）的基因组序列位于同源蛋白肝脏细胞粘附分子（L-CAM）翻译起始位点上游约600个碱基对处。K-CAM基因的11个外显子大小与L-CAM（肝细胞粘附分子）基因的外显子大小几乎相同，外显子与内含子的交界处位于完全相同的位置。然而，大多数内含子的大小和序列差异要大得多。对这两个基因更详细的比较表明，最后两个外显子（外显子15和16）的序列比其他任何外显子都更为相似；事实上，它们几乎完全相同。在这两个基因中分隔这些外显子的内含子彼此之间的相似性也远高于其他任何相应的内含子。这种相似程度似乎远远超过了因蛋白质结构选择所能解释的范围，这强烈表明在这两个基因复制并分化以执行不同生物学功能之后，它们之间发生了基因转换事件。
