Conti Chiara, Herrick John, Bensimon Aaron
Genomic Vision, 27 rue du Faubourg Saint Jacques, 75014 Paris, France.
Genes Chromosomes Cancer. 2007 Aug;46(8):724-34. doi: 10.1002/gcc.20448.
Oncogene amplification is a critical step leading to tumorigenesis, but the underlying mechanisms are still poorly understood. Despite data suggesting that DNA replication is a major source of genomic instability, little is known about replication origin usage and replication fork progression in rearranged regions. Using a single DNA molecule approach, we provide here the first study of replication kinetics on a previously characterized MYC/papillomavirus (HPV18) amplicon in a cervical cancer. Using this amplicon as a model, we investigated the role DNA replication control plays in generating amplifications in human cancers. The data reveal severely perturbed DNA replication kinetics in the amplified region when compared with other regions of the same genome. It was found that DNA replication is initiated from both genomic and viral sequences, resulting in a higher median frequency of origin firings. In addition, it was found that the higher initiation frequency was associated with an equivalent increase in the number of stalled replication forks. These observations raise the intriguing possibility that unscheduled replication origin activation at inserted HPV-18 viral DNA sequences triggers DNA amplification in this cancer cell line and the subsequent overexpression of the MYC oncogene.
癌基因扩增是导致肿瘤发生的关键步骤，但其潜在机制仍知之甚少。尽管有数据表明DNA复制是基因组不稳定的主要来源，但对于重排区域中复制起点的使用和复制叉的进展情况却知之甚少。我们采用单分子DNA方法，首次对宫颈癌中一个先前已鉴定的MYC/人乳头瘤病毒（HPV18）扩增子的复制动力学进行了研究。以该扩增子为模型，我们研究了DNA复制控制在人类癌症中产生扩增的作用。数据显示，与同一基因组的其他区域相比，扩增区域的DNA复制动力学受到严重干扰。研究发现，DNA复制起始于基因组序列和病毒序列，导致复制起点激活的中位频率更高。此外，还发现较高的起始频率与停滞复制叉数量的同等增加有关。这些观察结果提出了一个有趣的可能性，即插入的HPV-18病毒DNA序列上计划外的复制起点激活触发了该癌细胞系中的DNA扩增以及随后MYC癌基因的过表达。
