Sorkin B C, Gallin W J, Edelman G M, Cunningham B A
Rockefeller University, New York, NY 10021.
Proc Natl Acad Sci U S A. 1991 Dec 15;88(24):11545-9. doi: 10.1073/pnas.88.24.11545.
Genomic sequences immediately upstream of the translational start site for the chicken liver cell adhesion molecule (L-CAM) gene contain a second closely related gene, which, because of its location, we have designated the K-CAM gene. Less than 700 base pairs separate the presumed poly(A) site in the K-CAM gene from the translation initiation site for L-CAM. The sizes of exons 4-15 of the K-CAM gene are almost identical to those in the L-CAM gene and the exon/intron junctions occur at exactly equivalent positions in both genes. Exon 16, which includes the 3' untranslated region, is much shorter in the K-CAM gene and intron sizes and sequences are not generally conserved between the two genes. Probes from the K-CAM gene hybridized to a 3-kilobase mRNA that was present at high levels in embryonic skin, at lower levels in kidney, heart, and gizzard, and at still lower levels in brain and liver, as determined by Northern blotting. The sequence of the predicted gene product was nearly identical to that of the chicken B-cadherin cDNA, although the distribution of the K-CAM gene transcript differed from that reported for the cadherin. The proximity and identical overall structure of the K-CAM and L-CAM genes strongly suggest that they arose by gene duplication and raise the possibility that genes for other calcium-dependent CAMs may be located in clusters. Moreover, the tandem arrangement of the genes may have important implications for the regulation of their expression.
鸡肝细胞粘附分子（L-CAM）基因翻译起始位点上游的基因组序列包含另一个紧密相关的基因，鉴于其位置，我们将其命名为K-CAM基因。K-CAM基因中推测的聚腺苷酸化位点与L-CAM的翻译起始位点之间的距离不到700个碱基对。K-CAM基因第4至15外显子的大小与L-CAM基因中的几乎相同，并且两个基因中外显子/内含子的连接点恰好位于等效位置。包含3'非翻译区的第16外显子在K-CAM基因中要短得多，并且两个基因之间内含子的大小和序列通常不保守。通过Northern印迹法测定，K-CAM基因的探针与一个3千碱基的mRNA杂交，该mRNA在胚胎皮肤中高水平存在，在肾脏、心脏和砂囊中较低水平存在，在脑和肝脏中水平更低。预测的基因产物序列与鸡B-钙粘着蛋白cDNA的序列几乎相同，尽管K-CAM基因转录本的分布与报道的钙粘着蛋白不同。K-CAM和L-CAM基因的紧密相邻和相同的整体结构强烈表明它们是通过基因复制产生的，并增加了其他钙依赖性细胞粘附分子基因可能成簇定位的可能性。此外，基因的串联排列可能对其表达调控具有重要意义。
