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

染色体不稳定(CIN)导致的染色体异常在人类癌症和其他人类疾病中非常普遍。CIN分为结构CIN(S-CIN)和数字CIN(W-CIN)。虽然S-CIN可以由DNA复制过程中的缺陷引发，这种情况被称为复制应激(RS)，但有丝分裂功能障碍可能是W-CIN的原因。初步证据表明，S-CIN和W-CIN可能存在机械性连锁。事实上，出现有丝分裂错误和W-CIN的癌细胞也会受到复制压力的影响。在FOR2800的第一个资助期，我们发现W-CIN癌细胞具有温和的复制压力，足以在有丝分裂中引发整个染色体的错误分离。这是由有丝分裂纺锤体内异常的微管动力学所调节的，从而导致染色体错误分离。重要的是，我们发现复制动力学并没有减慢，而是RS引发的休眠起源激发的增加是有丝分裂缺陷和W-CIN的原因。事实上，选择性地诱导休眠起源放电足以引起W-CIN，令人惊讶的是，这需要激活DNA损伤诱导的ATM信号。此外，在与Maik Kschischo(FOR2800，SP3)的合作中，我们发现直接参与起始激发的基因在染色体不稳定的癌症标本中经常上调，它们的过度表达足以增加起始激发并诱导W-CIN。我们现在将在我们的结果的基础上，调查计划外起源激发如何导致整个染色体错误分离和W-CIN。我们将讨论ATM信号的作用，并研究DNA损伤是如何在休眠起源激发反应中诱导的。由于癌基因诱导的复制应激与异常起源激发有关，我们将调查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，我们将在结构和数字水平上调查起源激发和DNA损伤信号对基因组完整性的影响。

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.