NONMETHYLATED CPG-RICH ISLANDS AT THE HUMAN ALPHA-GLOBIN LOCUS - IMPLICATIONS FOR EVOLUTION OF THE ALPHA-GLOBIN PSEUDOGENE
NONMETHYLATED CPG-RICH ISLANDS AT THE HUMAN ALPHA-GLOBIN LOCUS - IMPLICATIONS FOR EVOLUTION OF THE ALPHA-GLOBIN PSEUDOGENE
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DOI：
10.1002/j.1460-2075.1987.tb04851.x
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发表时间：
1987-04-01
期刊：
影响因子：
11.4
通讯作者：
HIGGS, DR
中科院分区：
文献类型：
--
作者：
BIRD, AP;TAGGART, MH;HIGGS, DR
我们分析了人类部分α基因的CpG频率和CpG甲基化。球蛋白轨迹。在。alpha。1和。2个基因类似于哺乳动物“管家”基因特征的“hpai微小片段（HTF）岛”：CpG频率不受抑制；来自红系或非红系组织的DNA中可检测的CpGs不被甲基化，尽管侧翼的CpGs被甲基化；CpG集群是。apprx。长度为1.5 KB，并延伸到.alpha.的上游和下游。-珠蛋白转录起始位点。这些特征在β基因中没有发现。球蛋白轨迹。.alpha。-珠蛋白假基因（.psi…alpha.1）与。alpha.1高度同源。2和。1个基因，但缺乏HTF岛。序列比较表明，. α。2个基因在假基因中被TpG或CpA取代。这强烈表明，在假基因上的一个祖先HTF岛在种系中被甲基化，并由于5-甲基胞嘧啶的易变性而丢失。
We have analysed CpG frequency and CpG methylation across part of the human .alpha.-globin locus. Clusters of CpG at the .alpha.1 and .alpha.2 genes resemble the ''HpaII tiny fragment (HTF) islands'' that are characteristic of mammalian ''housekeeping'' genes: CpG frequency is not suppressed; testable CpGs are not methylated in DNA from erythroid or non-erythroid tissues, although flanking CpGs are methylated; CpG clusters are .apprx. 1.5 kb long and extend both upstream and downstream of the .alpha.-globin transcription start site. These features are not found at genes of the .beta.-globin locus. The .alpha.-globin pseudogene (.psi..alpha.1) is highly homologous to the .alpha.2 and .alpha.1 genes, but it lacks an HTF island. Sequence comparison shows that a high proportion of CpGs in the .alpha.2 gene are substituted by TpG or CpA in the pseudogene. This strongly suggests that an ancestral HTF island at the pseudogene became methylated in the germline, and was lost due to the mutability of 5-methylcytosine.