The metabolic engineering of microorganisms is an attractive platform for bioremediation and the industrial production of chemicals. However, biocontainment strategies are needed if genetically modified organisms are to be released into open environments. Hoffmann and Cai report a biocontainment strategy in yeast based on targeted protein degradation.

The authors performed high-throughput screening to identify genes that, when fused to an estrogen receptor-derived degron (ERdd), made Saccharomyces cerevisiae dependent on the hormone estradiol. Estradiol stabilizes the ERdd fusion protein, preventing its degradation. They identified three top strains expressing the genes SPC110–ERdd, RRP46–ERdd and DIS3–ERdd that were strictly dependent on estradiol. The growth of a strain with both SPC110–ERdd and RRP46–ERdd could be restored to the fitness level of the wild-type parental strain when treated with 100 nM estradiol. The wild-type strain did not outcompete the engineered strains over 100 generations, suggestive of their evolutionary stability, which is crucial for open-environment applications. Analysis of strains able to escape biocontainment showed mutations in fusion proteins that inactivate the ERdd and in proteins that affect regulation of the proteasome.

微生物代谢工程是生物修复和化学品工业生产的一个有吸引力的平台。然而，如果要将转基因生物释放到开放环境中，就需要采取生物遏制策略。 Hoffmann 和 Cai 报告了一种基于目标蛋白质降解的酵母生物防护策略。

作者进行了高通量筛选，以确定当与雌激素受体衍生的降解决定子 (ERdd) 融合时，使酿酒酵母依赖于雌二醇激素的基因。雌二醇可稳定 ERdd 融合蛋白，防止其降解。他们确定了三个表达基因SPC110–ERdd、RRP46–ERdd和DIS3–ERdd 的顶级菌株，这些菌株严格依赖于雌二醇。当用 100 nM 雌二醇处理时，同时具有SPC110-ERdd和RRP46-ERdd 的菌株的生长可以恢复到野生型亲本菌株的适合水平。野生型菌株在超过 100 代的竞争中并未击败工程菌株，这表明它们的进化稳定性，这对于开放环境应用至关重要。对能够逃脱生物防护的菌株的分析表明，融合蛋白中存在使 ERdd 失活的突变，以及影响蛋白酶体调节的蛋白质中的突变。