Barsyte-Lovejoy Dalia, Lau Suzanne K, Boutros Paul C, Khosravi Fereshteh, Jurisica Igor, Andrulis Irene L, Tsao Ming S, Penn Linda Z
Division of Cancer Genomics and Proteomics, Ontario Cancer Institute/Princess Margaret Hospital, University of Toronto, Toronto, Canada.
Cancer Res. 2006 May 15;66(10):5330-7. doi: 10.1158/0008-5472.CAN-06-0037.
The product of the MYC oncogene is widely deregulated in cancer and functions as a regulator of gene transcription. Despite an extensive profile of regulated genes, the transcriptional targets of c-Myc essential for transformation remain unclear. In this study, we show that c-Myc significantly induces the expression of the H19 noncoding RNA in diverse cell types, including breast epithelial, glioblastoma, and fibroblast cells. c-Myc binds to evolutionarily conserved E-boxes near the imprinting control region to facilitate histone acetylation and transcriptional initiation of the H19 promoter. In addition, c-Myc down-regulates the expression of insulin-like growth factor 2 (IGF2), the reciprocally imprinted gene at the H19/IGF2 locus. We show that c-Myc regulates these two genes independently and does not affect H19 imprinting. Indeed, allele-specific chromatin immunoprecipitation and expression analyses indicate that c-Myc binds and drives the expression of only the maternal H19 allele. The role of H19 in transformation is addressed using a knockdown approach and shows that down-regulation of H19 significantly decreases breast and lung cancer cell clonogenicity and anchorage-independent growth. In addition, c-Myc and H19 expression shows strong association in primary breast and lung carcinomas. This work indicates that c-Myc induction of the H19 gene product holds an important role in transformation.
MYC癌基因的产物在癌症中广泛失调,并作为基因转录的调节因子发挥作用。尽管已对受调控基因进行了广泛分析,但对于c-Myc转化所必需的转录靶点仍不清楚。在本研究中,我们发现c-Myc在多种细胞类型中显著诱导H19非编码RNA的表达,包括乳腺上皮细胞、胶质母细胞瘤细胞和成纤维细胞。c-Myc与印记控制区域附近进化保守的E盒结合,以促进H19启动子的组蛋白乙酰化和转录起始。此外,c-Myc下调胰岛素样生长因子2(IGF2)的表达,IGF2是H19/IGF2基因座上相互印记的基因。我们发现c-Myc独立调节这两个基因,且不影响H19印记。事实上,等位基因特异性染色质免疫沉淀和表达分析表明,c-Myc仅结合并驱动母本H19等位基因的表达。我们采用敲低方法研究了H19在转化中的作用,结果表明H19的下调显著降低了乳腺癌和肺癌细胞的克隆形成能力及非锚定依赖性生长。此外,c-Myc和H19的表达在原发性乳腺癌和肺癌中显示出强相关性。这项工作表明,c-Myc对H19基因产物的诱导在转化中起重要作用。