Factors that modulate cellular homeostasis to overcome replicative stress in aging

我们已经检查了不同化合物对在强阻断处停滞的单个复制叉的频率的活性。现将最近的一些结果总结如下： 我们已经发现，用于癌症治疗的聚ADP核糖合成抑制剂增加了单叉停滞的频率。 相比之下，抑制聚ADP核糖的降解降低了单失速叉的频率。 增强蛋白质伴侣活性的化合物改善了正确的蛋白质折叠，也降低了单叉停滞事件的频率。 我们的研究结果表明，一些小分子效应物可以在基因组水平上影响事件，使得基因组不稳定和应激诱导事件的频率降低。我们计划测试其他化合物，并将跟踪那些在试验中显示活性的化合物。 我们还表明，可以在鼠造血干细胞（HSC）中进行测定。这使得研究“抗衰老”化合物对来自年轻和老年供体的干细胞抵抗复制压力的能力的影响成为可能。我们发现，与年轻供体相比，老年造血干细胞中单叉停滞事件的频率升高。此外，我们还研究了可以观察到单叉失速事件增加的年龄。值得注意的是，这似乎相当于中年小鼠。因此，似乎在这种小鼠干细胞模型中，细胞克服复制阻断的能力在它们达到“老化”状态之前就下降了。 最近，我们发现有两种形式的复制体遇到了块。一个在S期早期和常染色质中有活性，另一个在S期晚期和异染色质中有活性。我们现在要问的是，单叉停滞事件的增加是否发生在基因组的一个或另一个或两个区域。

We have examined the activity of different compounds on the frequency of single replication forks stalled at a strong block. Some recent results are summarized here: We have found that inhibitors of poly ADP ribose synthesis, which are used in cancer therapy, increase the frequency of single fork stalling. In contrast, inhibition of the degradation of poly ADP ribose reduces the frequency of single stalled forks. A compound that enhances the activity of a protein chaperone that improves correct protein folding also reduces the frequency of single fork stalling events. Our results suggest that some small molecule effectors can influence events at the level of the genome, such that the frequency of a genome destabilizing and stress inducing event is reduced. We plan to test additional compounds, and will follow those that show activity in the assay. We have also shown that assay can be performed in murine hematopoietic stem cells (HSCs). This makes it possible to examine the influence of "anti aging" compounds on the competence of stem cells, from young and old donors, to resist replication stress. We find that the frequency of single fork stalling events rises in HSCs from old as compared to young donors. Furthermore, we have examined the age at which the increase in single fork stalling events can be observed. Remarkably this appears at an equivalent to middle age in mice. Consequently it appears that in this mouse stem cell model cellular competence to overcome replication blocks declines well before they reach an "aged" status. Recently, we found that there are two forms of the replisomes that encounter the block. One is active in early S phase and in euchromatin, the other in late S phase and in heterochromatin. We are now asking if the increase in single fork stalling events occurs in one or the other or both regions of the genome.