Nusse R, Theunissen H, Wagenaar E, Rijsewijk F, Gennissen A, Otte A, Schuuring E, van Ooyen A
Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam.
Mol Cell Biol. 1990 Aug;10(8):4170-9. doi: 10.1128/mcb.10.8.4170-4179.1990.
Wnt-1 (int-1) is a cellular oncogene often activated by insertion of proviral DNA of the mouse mammary tumor virus. We have mapped the 5' end and the promoter area of the Wnt-1 gene by nuclease protection and primer extension assays. In differentiating P19 embryonal carcinoma cells, in which Wnt-1 is naturally expressed, two start sites of transcription were found, one preceded by two TATA boxes and one preceded by several GC boxes. In P19 cells, a 1-kilobase upstream sequence of Wnt-1 was able to confer differentiation-specific expression on a heterologous gene. We have investigated how Wnt-1 transcription was affected by mouse mammary tumor virus proviral integrations in various configurations near the promoters of the gene. One provirus has been inserted in the 5' nontranslated part of Wnt-1, in the same transcriptional orientation, and has functionally replaced the Wnt-1 promoters. Wnt-1 transcription in this tumor starts in the right long terminal repeat of the provirus, with considerable readthrough transcription from the left long terminal repeat. Another provirus has been inserted in the orientation opposite that of Wnt-1 into a GC box, disrupting the first Wnt-1 transcription start site but not the downstream start site. Most insertions have not structurally altered the Wnt-1 transcripts and have enhanced the activity of the normal two promoters.
Wnt-1（int-1）是一种细胞癌基因，常因小鼠乳腺肿瘤病毒前病毒DNA的插入而被激活。我们通过核酸酶保护和引物延伸分析对Wnt-1基因的5'末端和启动子区域进行了定位。在Wnt-1自然表达的分化型P19胚胎癌细胞中，发现了两个转录起始位点，一个前面有两个TATA盒，另一个前面有几个GC盒。在P19细胞中，Wnt-1上游1千碱基的序列能够赋予异源基因分化特异性表达。我们研究了Wnt-1转录如何受到基因启动子附近各种构型的小鼠乳腺肿瘤病毒前病毒整合的影响。一个前病毒已插入Wnt-1的5'非翻译区，转录方向相同，并在功能上取代了Wnt-1启动子。该肿瘤中Wnt-1的转录起始于前病毒的右长末端重复序列，同时有大量来自左长末端重复序列的通读转录。另一个前病毒以与Wnt-1相反的方向插入一个GC盒，破坏了第一个Wnt-1转录起始位点，但未破坏下游起始位点。大多数插入并未在结构上改变Wnt-1转录本，反而增强了正常两个启动子的活性。
