Rogers M A, Winter H, Wolf C, Heck M, Schweizer J
German Cancer Research Center, Research Program 2, Im Neuenheimerfeld 280, 691200 Heidelberg, Germany.
J Biol Chem. 1998 Oct 9;273(41):26683-91. doi: 10.1074/jbc.273.41.26683.
Polymerase chain reaction-based screening of an arrayed human P1 artificial chromosome (PAC) library using primer pairs specific for the human type I hair keratins hHa3-II or hHa6, led to the isolation of two PAC clones, which covered 190 kilobase pairs (kbp) of genomic DNA and contained nine human type I hair keratin genes, one transcribed hair keratin pseudogene, as well as one orphan exon. The hair keratin genes are 4-7 kbp in size, exhibit intergenic distances of 5-8 kbp, and display the same direction of transcription. With one exception, all hair keratin genes are organized into 7 exons and 6 positionally conserved introns. On the basis of sequence homologies, the genes can be grouped into three subclusters of tandemly arranged genes. One subcluster harbors the highly related genes hHa1, hHa3-I, hHa3-II, and hHa4. A second subcluster of highly related genes comprises the novel genes hHa7 and hHa8, as well as pseudogene PsihHaA, while the structurally less related genes hHa6, hHa5, and hHa2 are constituents of the third subcluster. As shown by reverse transcription-polymerase chain reaction, all hair keratin genes, including the pseudogene, are expressed in the human hair follicle. The transcribed pseudogene PsihHaA contains a premature stop codon in exon 4 and exhibits aberrant pre-mRNA splicing. Evolutionary tree construction reveals an early divergence of hair keratin genes from cytokeratin genes, followed by the segregation of the genes into the three subclusters. We suspect that the 190-kbp domain contains the entire complement of human type I hair keratin genes.
利用针对人类I型毛发角蛋白hHa3-II或hHa6的引物对，基于聚合酶链反应筛选一个有序排列的人类P1人工染色体（PAC）文库，从而分离出两个PAC克隆，它们覆盖了190千碱基对（kbp）的基因组DNA，包含9个人类I型毛发角蛋白基因、一个转录的毛发角蛋白假基因以及一个孤儿外显子。这些毛发角蛋白基因大小为4 - 7 kbp，基因间距离为5 - 8 kbp，且转录方向相同。除一个例外，所有毛发角蛋白基因均由7个外显子和6个位置保守的内含子组成。基于序列同源性，这些基因可分为三个串联排列基因的亚簇。一个亚簇包含高度相关的基因hHa1、hHa3-I、hHa3-II和hHa4。高度相关基因的第二个亚簇包括新基因hHa7和hHa8以及假基因PsihHaA，而结构相关性较低的基因hHa6、hHa5和hHa2是第三个亚簇的组成部分。如逆转录 - 聚合酶链反应所示，所有毛发角蛋白基因，包括假基因，均在人类毛囊中表达。转录的假基因PsihHaA在第4外显子中含有一个提前终止密码子，并表现出异常的前体mRNA剪接。进化树构建显示毛发角蛋白基因与细胞角蛋白基因早期分化，随后基因分离为三个亚簇。我们推测这个190 - kbp的区域包含了人类I型毛发角蛋白基因的全部互补序列。
