SP2: Molecular mechanisms of replication stress-induced mitotic chromosome missegregation

导致染色体畸变的染色体不稳定性（CIN）在人类癌症和其他人类疾病中高度流行。CIN分为结构性CIN（S-CIN）和数值性CIN（W-CIN）。虽然S-CIN可以由DNA复制过程中的缺陷触发，这种情况称为复制应激（RS），但有丝分裂功能障碍可以解释W-CIN。第一个证据表明，S-CIN和W-CIN可能是机械联系。事实上，显示有丝分裂错误和W-CIN的癌细胞也遭受复制应激。在FOR 2800的第一个资助期内，我们发现W-CIN癌细胞的特征是轻度复制应激，足以引发有丝分裂中的整个染色体错误分离。这是由有丝分裂纺锤体内异常微管动力学介导的，导致染色体错误分离。重要的是，我们发现，不是减慢复制动力学，而是由RS触发的休眠起源放电的增加是有丝分裂缺陷和W-CIN的原因。事实上，选择性诱导休眠起源放电足以引起W-CIN，并且令人惊讶的是，这需要激活DNA损伤诱导的ATM信号传导。此外，在与Maik Kschischo（FOR 2800，SP3）的合作中，我们发现直接参与起源放电的基因在染色体不稳定的癌症标本中经常上调，并且它们的过表达足以增加起源放电并诱导W-CIN。我们现在将建立在我们的结果，并将调查如何非计划的起源射击导致整个染色体的错误分离和W-CIN。我们将讨论ATM信号的作用，并研究如何诱导DNA损伤，以响应休眠的起源射击。由于癌基因诱导的复制应激与异常的原点放电有关，我们将研究癌基因激活是否以及如何导致W-CIN，以及其他形式的DNA损伤是否也导致有丝分裂错误。最后，我们将研究起源发射和DNA损伤信号对基因组完整性的影响，无论是在结构上还是在数值上。

Chromosome instability (CIN) leading to chromosome aberrations is highly prevalent in human cancer and other human diseases. CIN is categorized into structural CIN (S-CIN) and numerical CIN (W-CIN). While S-CIN can be triggered by defects during DNA replication, a condition known as replication stress (RS), mitotic dysfunction can account for W-CIN. First evidence indicated that S-CIN and W-CIN might be mechanistically linked. In fact, cancer cells showing mitotic errors and W-CIN also suffer from replication stress. During the first funding period of the FOR2800, we found that W-CIN cancer cells are characterized by mild replication stress that is sufficient to trigger whole chromosome missegregation in mitosis. This is mediated by abnormal microtubule dynamics within mitotic spindles that leads to chromosome missegregation. Importantly, we discovered that not slowed replication kinetics, but rather an increase in dormant origin firing that is triggered by RS is responsible for the mitotic defects and for W-CIN. In fact, selective induction of dormant origin firing is sufficient to cause W-CIN and, surprisingly, this requires the activation of DNA damage-induced ATM-signaling. Moreover, in collaboration with Maik Kschischo (FOR2800, SP3) we found that genes directly involved in origin firing are frequently upregulated in chromosomally unstable cancer specimens and their overexpression is sufficient to increase origin firing and to induce W-CIN. We will now build on our results and will investigate how unscheduled origin firing causes whole chromosome missegregation and W-CIN. We will address the role of ATM signaling and investigate how DNA damage is induced in response to dormant origin firing. Since oncogene-induced replication stress has been linked to abnormal origin firing, we will investigate whether and how oncogene activation contributes to W-CIN and whether other forms of DNA damage are also contributing to mitotic errors. Finally, we will investigate the consequences of origin firing and DNA damage signaling on the integrity of the genome, both on a structural and numerical level.