Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er Sheva, Israel.
PLoS Biol. 2010 Oct 12;8(10):e1000507. doi: 10.1371/journal.pbio.1000507.
The robustness of complex biological processes in the face of environmental and genetic perturbations is a key biological trait. However, while robustness has been extensively studied, little is known regarding the fragility of biological processes. Here, we have examined the susceptibility of DNA replication and repair processes mediated by the proliferating cell nuclear antigen (PCNA). Using protein directed evolution, biochemical, and genetic approaches, we have generated and characterized PCNA mutants with increased affinity for several key partners of the PCNA-partner network. We found that increases in PCNA-partner interaction affinities led to severe in vivo phenotypic defects. Surprisingly, such defects are much more severe than those induced by complete abolishment of the respective interactions. Thus, the subtle and tunable nature of these affinity perturbations produced different phenotypic effects than realized with traditional "on-off" analysis using gene knockouts. Our findings indicate that biological systems can be robust to one set of perturbations yet fragile to others.
复杂生物过程在面对环境和遗传干扰时的稳健性是一个关键的生物学特性。然而，尽管已经广泛研究了稳健性，但对于生物过程的脆弱性却知之甚少。在这里，我们研究了增殖细胞核抗原 (PCNA) 介导的 DNA 复制和修复过程的易感性。我们使用蛋白质定向进化、生化和遗传方法，生成并表征了 PCNA 突变体，这些突变体与 PCNA-伙伴网络的几个关键伙伴的亲和力增加。我们发现，增加 PCNA-伙伴相互作用的亲和力会导致严重的体内表型缺陷。令人惊讶的是，这些缺陷比完全消除各自相互作用所引起的缺陷严重得多。因此，这些亲和力扰动的细微和可调性质产生的表型效应与使用基因敲除的传统“开-关”分析不同。我们的研究结果表明，生物系统可以对一组干扰具有稳健性，而对另一组干扰则很脆弱。
