Wang Jie, Bhutani Manisha, Pathak Ashutosh K, Lang Wenhua, Ren Hening, Jelinek Jaroslav, He Rong, Shen Lanlan, Issa Jean-Pierre, Mao Li
Department of Thoracic/Head and Neck Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Cancer Res. 2007 Nov 15;67(22):10647-52. doi: 10.1158/0008-5472.CAN-07-1337.
DNA methyltransferase 3B (DNMT3B) is critical in de novo DNA methylation during development and tumorigenesis. We recently reported the identification of a DNMT3B subfamily, DeltaDNMT3B, which contains at least seven variants, resulting from alternative pre-mRNA splicing. DeltaDNMT3Bs are the predominant expression forms of DNMT3B in human lung cancer. A strong correlation was observed between the promoter methylation of RASSF1A gene but not p16 gene (both frequently inactivated by promoter methylation in lung cancer) and expression of DeltaDNMT3B4 in primary lung cancer, suggesting a role of DeltaDNMT3B in regulating promoter-specific methylation of common tumor suppressor genes in tumorigenesis. In this report, we provide first experimental evidence showing a direct involvement of DeltaDNMT3B4 in regulating RASSF1A promoter methylation in human lung cancer cells. Knockdown of DeltaDNMT3B4 expression by small interfering RNA resulted in a rapid demethylation of RASSF1A promoter and reexpression of RASSF1A mRNA but had no effect on p16 promoter in the lung cancer cells. Conversely, normal bronchial epithelial cells with stably transfected DeltaDNMT3B4 gained an increased DNA methylation in RASSF1A promoter but not p16 promoter. We conclude that promoter DNA methylation can be differentially regulated and DeltaDNMT3Bs are involved in regulation of such promoter-specific de novo DNA methylation.
DNA甲基转移酶3B（DNMT3B）在发育和肿瘤发生过程中的DNA从头甲基化中起关键作用。我们最近报道了一个DNMT3B亚家族DeltaDNMT3B的鉴定，它包含至少七个变体，是由前体mRNA的可变剪接产生的。DeltaDNMT3B是DNMT3B在人类肺癌中的主要表达形式。在原发性肺癌中，观察到RASSF1A基因而非p16基因（两者在肺癌中都经常因启动子甲基化而失活）的启动子甲基化与DeltaDNMT3B4的表达之间存在很强的相关性，这表明DeltaDNMT3B在肿瘤发生过程中调节常见肿瘤抑制基因启动子特异性甲基化中发挥作用。在本报告中，我们提供了首个实验证据，表明DeltaDNMT3B4直接参与调节人类肺癌细胞中RASSF1A启动子的甲基化。用小干扰RNA敲低DeltaDNMT3B4的表达导致RASSF1A启动子快速去甲基化和RASSF1A mRNA重新表达，但对肺癌细胞中的p16启动子没有影响。相反，稳定转染DeltaDNMT3B4的正常支气管上皮细胞在RASSF1A启动子中DNA甲基化增加，但在p16启动子中没有增加。我们得出结论，启动子DNA甲基化可以被差异调节，并且DeltaDNMT3B参与了这种启动子特异性DNA从头甲基化的调节。
