Synthetic gene circuits enable quantitative comparison of proteosynthesis rates in mammalian cells

Transcription and translation may vary significantly among mammalian cell types. Such differences may be important for comprehensively understanding cellular homeostasis and responses in various conditions. Here, we establish a synthetic biological framework to enable such comparisons. To minimize the random effects of genomic integration, we performed site-specific recombination （SSR）by applying FLPe recombinase-mediated cassette exchange (RMCE) to integrate single genes or gene circuits into the same “genomic safe harbor” locus AAVS1 in multiple mammalian cell lines. Upon establishing stable cell lines, we charted and compared the constitutive and inducer-dependent proteosynthesis levels using the eGFP reporter, and characterized the fold change, coefficient of variation (CV), expression kinetics based on the proliferation rate of each cell type. Overall, our study provided a systematic approach to quantify the variation of proteosynthesis due to the activity of the transcription and translation machinery in various mammalian cell types, allowing a better understanding of cell state diversity, which may be useful in mammalian biosystem modeling.