Human delta-aminolevulinate dehydratase (ALAD) gene: structure and alternative splicing of the erythroid and housekeeping mRNAs.
Human delta-aminolevulinate dehydratase (ALAD) gene: structure and alternative splicing of the erythroid and housekeeping mRNAs.
复制标题
人 δ-氨基乙酰丙酸脱水酶 (ALAD) 基因：红系和管家 mRNA 的结构和选择性剪接。
DOI：
10.1006/geno.1994.1054
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发表时间：
1994
期刊：
影响因子：
4.4
通讯作者：
Wetmur,JG
中科院分区：
文献类型：
--
作者：
Kaya,AH;Plewinska,M;Wong,DM;Desnick,RJ;Wetmur,JG
分离含有人δ-氨基酮戊酸脱氢酶（ALAD）（血红素途径中的第二种酶）的生成克隆，并在两个方向上测定整个序列（15，913 bp; GenBank登录号X64467）。该基因包含两个可选的非编码外显子1A和1B，以及11个编码外显子2-12。基因内有一个持续重复的元件，包括一个可能由基因转换引起的反向重复序列。管家转录，其中包括外显子1A和不1B，被确定在人类成人肝脏cDNA文库，而红细胞特异性转录，其中包含外显子1B和不1A，被检测到在人类K562红白血病cDNA文库。持家外显子1A上游的启动子区域富含GC，包含三个潜在的Sp1元件和一个CCAAT盒。在更上游，存在三个潜在的加塔-1结合位点和一个AP 1位点。红细胞特异性外显子1B上游的启动子区有几个CACCC盒和两个潜在的加塔-1结合位点。为了评估外显子1A和1B的组织特异性表达，用含有外显子1A或1B及其各自上游启动子区的CAT构建体转导HeLa和K562细胞。两个管家CAT构建体，外显子1A上游450和1400 bp，在HeLa细胞中以相似的水平表达，而红细胞特异性构建体，包含外显子1B上游的整个450 bp启动子区域，没有。相反，管家和红细胞构建体都在K562细胞中表达。这些发现表明，人类ALAD基因包含两个启动子区域，通过选择性剪接产生管家和红系特异性转录物，类似于人类羟甲基胆烷合酶基因的表达，其编码海涅生物合成途径的第三种酶。管家和红细胞特异性转录本的新表达显然是为了确保足够的海涅碱生物合成，以高水平的组织特异性生产生命所需的血红蛋白。
Generate clones containing human δ-aminolevuliuate dehydratase (ALAD), the second enzyme in the heme pathway, were isolated, and the entire sequence was determined in both orientations (15,913 bp; GenBank Accession No. X64467). The gene contained two alternative noncoding exons, 1A and 1B, and 11 coding exons, 2-12. TenAlu-repetitive elements were within the gene, including an inverted repeat that may have resulted from gene conversion. The housekeeping transcript, which included exon 1A and not 1B, was identified in a human adult liver cDNA library, while an erythroid-specific transcript, which contained exon 1B and not 1A, was detected in a human K562 erythroleukemia cDNA library. The promoter region upstream of housekeeping exon 1A was GC-rich and contained three potential Sp1 elements and a CCAAT box. Further upstream, there were three potential GATA-1 binding sites and an AP1 site. The promoter region upstream of erythroid-specific exon 1B had several CACCC boxes and two potential GATA-1 binding sites. To assess the tissue-specific expression of exerts 1A and 1B, HeLa and K562 cells were transduced with CAT constructs containing either exon 1A or 1B and their respective upstream promoter region. Two housekeeping CAT constructs, with 450 and 1400 bp upstream of exon 1A, wereexpressed at similar levels in HeLa cells, whereas the erythroid-specific construct, containing the entire 450-bp promoter region upstream of exon 1B, was not. In contrast, the housekeeping and erythroid constructs were both expressed in K562 cells. These findings demonstrate that the human ALAD gene contains two promoter regions that generate housekeeping and erythroid-specific transcripts by alternative splicing, analogous to the expression of the human hydroxymethylbilane synthase gene, which encodes the third enzyme of the heine biosynthetic pathway. The novel expression of housekeeping and erythroid-specific transcripts apparently evolved to ensure sufficient heine biosynthesis for the high-level tissue-specific production of hemoglobin required for life.