Kok K, Van den Berg A, Veldhuis P M, Franke M, Terpstra P, Buys C H
Department of Medical Genetics, University of Groningen, The Netherlands.
Gene Expr. 1995;4(3):163-75.
The human UBE1L gene, for which the product may well play a role in the ubiquitin system because of its high degree of identity to the ubiquitin activating enzyme, is located at 3p21, a chromosomal region consistently showing loss of heterozygosity in lung cancer. The finding that UBE1L is well expressed in normal lung tissue, but hardly or not in lung cancer-derived cell lines, prompted us to investigate its genomic structure to find an explanation for the lack of expression in lung cancer. The gene has 22 exons distributed over 8.4 kb. Both anchored PCR experiments and mapping of DNase I-hypersensitive sites point to the region immediately upstream of exon 1 as the promoter site. Three moderately to well-informative polymorphisms were found, of which one is easily directly detectable. Cancer-specific mutations were not detected. The lack of expression in lung cancer cell lines correlated with a highly decreased sensitivity towards DNAse I of the promoter region and with an almost complete methylation of the HhaI site in the first exon. 5'-Azacytidine-induced demethylation did not result in a marked increase of the UBE1L mRNA level in the tumor cell lines. This leaves the possibility that mutation or absence of yet unknown transcription factors causes a regulatory block of the UBE1L gene.
人类UBE1L基因位于3p21，该区域在肺癌中一直显示杂合性缺失，因其与泛素激活酶高度同源，其产物很可能在泛素系统中发挥作用。UBE1L在正常肺组织中表达良好，但在肺癌衍生的细胞系中几乎不表达或不表达，这一发现促使我们研究其基因组结构，以寻找肺癌中缺乏表达的原因。该基因有22个外显子，分布在8.4 kb区域。锚定PCR实验和DNase I超敏位点图谱均表明外显子1上游紧邻区域为启动子位点。发现了三个中度至高度信息丰富的多态性，其中一个易于直接检测。未检测到癌症特异性突变。肺癌细胞系中缺乏表达与启动子区域对DNAse I的敏感性高度降低以及第一个外显子中HhaI位点几乎完全甲基化相关。5'-氮杂胞苷诱导的去甲基化并未导致肿瘤细胞系中UBE1L mRNA水平显著增加。这使得未知转录因子的突变或缺失导致UBE1L基因调控受阻成为可能。
