Kolsto A B, Kollias G, Giguere V, Isobe K I, Prydz H, Grosveld F
Nucleic Acids Res. 1986 Dec 22;14(24):9667-78.
The Thy-1 gene is expressed in a tissue- and stage-specific pattern and has a typical 1.6kb methylation-free island (MFI) covering about 600bp upstream and downstream of the two alternative first exons. By microinjection of a mouse Thy-1.1/human Thy-1 gene into fertilized eggs, we were able to show that the MFI is restored in the transgenic mice. The flanking sequence became methylated, but the MFI remains unmethylated in all tissues of transgenic mice at different developmental stages tested, irrespective of the site of expression of the gene. There is one exception, in extra-embryonal tissues of 14.5 day embryos a small percentage of the islands were methylated. We conclude that maintenance of the MFI is regulated by cis-acting sequences present within the gene, and indicates that the unmethylated state of the islands is consistent with a necessary but not sufficient condition for expression of the gene.
Thy-1基因以组织和阶段特异性模式表达，并有一个典型的1.6kb无甲基化岛（MFI），覆盖两个可变的第一个外显子上下游约600bp区域。通过将小鼠Thy-1.1/人Thy-1基因显微注射到受精卵中，我们能够证明在转基因小鼠中MFI得以恢复。侧翼序列发生了甲基化，但在所测试的不同发育阶段的转基因小鼠的所有组织中，MFI仍保持未甲基化状态，与基因的表达位点无关。有一个例外，在14.5天胚胎的胚外组织中，有一小部分岛发生了甲基化。我们得出结论，MFI的维持受基因内存在的顺式作用序列调控，这表明岛的未甲基化状态与基因表达的必要但非充分条件一致。
