Surguchov A, Bronson J D, Banerjee P, Knowles J A, Ruiz C, Subbaraya I, Palczewski K, Baehr W
Moran Eye Center, University of Utah Health Science Center, Salt Lake City 84132, USA.
Genomics. 1997 Feb 1;39(3):312-22. doi: 10.1006/geno.1996.4513.
GCAP1 and GCAP2 are related Ca(2+)-binding proteins that activate photoreceptor guanylate cyclase(s). We showed previously that the human GCAP1 gene, consisting of four exons, is located at 6p21.1 (locus designation GUCA). To identify the chromosomal location of the GCAP2 gene, we first cloned its cDNA and determined its intron-exon distribution by PCR analysis. The results show that the introns of the GCAP2 gene are positioned exactly as in the GCAP1 gene and are nearly double in size. Sequence similarity between the two genes, however, is limited to portions of exons 1 and 2. The GCAP1 and GCAP2 genes are transcribed into single mRNA species (1.7 and 2.2 kb, respectively) and are detectable only in the retina by Northern blotting. The GCAP2 gene was found by somatic human-hamster hybrid panel analysis and FISH to reside at GUCA in a region indistinguishable from that of GCAP1. PCR analysis with exon 4-specific primers showed that the genes are in a tail-to-tail array less than 5 kb apart and altogether span less than 20 kb of genomic DNA. The identical gene structures and loci of GCAP1 and GCAP2, and the identical function of the gene products, are consistent with gene duplication event.
GCAP1和GCAP2是相关的钙结合蛋白，可激活光感受器鸟苷酸环化酶。我们先前表明，由四个外显子组成的人类GCAP1基因位于6p21.1（基因座命名为GUCA）。为了确定GCAP2基因的染色体定位，我们首先克隆了其cDNA，并通过PCR分析确定了其内含子-外显子分布。结果表明，GCAP2基因的内含子位置与GCAP1基因完全相同，大小几乎是其两倍。然而，这两个基因之间的序列相似性仅限于外显子1和2的部分。GCAP1和GCAP2基因转录为单一的mRNA种类（分别为1.7和2.2 kb），通过Northern印迹法仅在视网膜中可检测到。通过体细胞人-仓鼠杂交面板分析和荧光原位杂交发现，GCAP2基因位于GUCA，其区域与GCAP1难以区分。用外显子4特异性引物进行的PCR分析表明，这两个基因呈尾对尾排列，相距不到5 kb，总共跨越不到20 kb的基因组DNA。GCAP1和GCAP2相同的基因结构和基因座，以及基因产物相同的功能，与基因复制事件一致。
