Delayed Replication Timing and the S-M Phase Checkpoint

描述（由申请人提供）：癌细胞与其正常细胞对应物在许多重要特征上不同，包括分化丧失、基因组不稳定性增加和药物敏感性降低。毫不奇怪，基因改变发生在大多数（如果不是所有）癌细胞中，并且被认为是这些表型改变的核心。此外，潜在的遗传不稳定性被认为是产生癌细胞中发生的多种遗传变化所必需的。我的实验室使用体细胞和分子遗传学来鉴定和表征在肿瘤细胞中发现的诱导异常细胞表型的遗传改变。通过利用这种方法，我的实验室已经确定了一个以前未知的染色体异常，与某些染色体重排。这种染色体表型的特征在于有丝分裂染色体浓缩延迟、染色体复制时间延迟、复制检查点激酶ATR的过表达和显著的染色体不稳定性。具有这种表型的染色体在肿瘤衍生细胞系和原发性肿瘤中很常见。此外，我们还发现具有这种表型的染色体激活DNA复制检查点（S-M期检查点）。我们的研究结果支持了一个模型，在肿瘤细胞中发现的染色体不稳定性源于某些染色体重排的复制时间缺陷。本提案中描述的实验旨在表征对这些异常染色体的细胞反应。该提案旨在：1）确定停滞或延迟的DNA复制导致ATR过表达的机制; 2）表征DNA复制检查点在DRT/DMC表型中所起的作用，以及3）确定具有DRT/DMC的染色体是否激活有丝分裂纺锤体检查点。

DESCRIPTION (provided by applicant): Cancer cells differ from their normal cellular counterparts in many important characteristics, including loss of differentiation, increased genomic instability, and decreased drug sensitivity. Not surprisingly, genetic alterations occur in most, if not all cancer cells, and are thought to lie at the heart of these phenotypic alterations. Furthermore, an underlying genetic instability is thought to be required to generate the multiple genetic changes that occur in cancer cells. My laboratory uses somatic cell and molecular genetics to identify and characterize genetic alterations found in tumor cells that induce abnormal cellular phenotypes. By utilizing this approach, my lab has identified a previously unknown chromosomal abnormality that is associated with certain chromosomal rearrangements. This chromosomal phenotype is characterized by a delay in mitotic chromosome condensation, a delay in the chromosome replication timing, over-expression of the replication checkpoint kinase ATR, and significant chromosomal instability. Chromosomes with this phenotype are common in tumor derived cell lines and in primary tumors. Furthermore, we have found that chromosomes with this phenotype activate the DNA replication checkpoint (S-M phase checkpoint). Our findings support a model in which the chromosomal instability found in tumor cells stems from a defect in the replication timing of certain chromosomal rearrangements. The experiments described in this proposal are designed to characterize the cellular response to these abnormal chromosomes. This proposal is designed to: 1) determine the mechanisms by which stalled or delayed DNA replication results in ATR over-expression; 2) characterize the role that the DNA replication checkpoint plays in the DRT/DMC phenotype, and 3) determine if chromosomes with DRT/DMC activate the mitotic spindle checkpoints.