Boutz, D. R. | bioRxiv Science

bioRxiv2017

Reduced protein expression in a virus attenuated by codon deoptimization

The engineering of hundreds of synonymous codon changes into a viral genome appears to provide a general means of achieving attenuation. The mechanistic underpinnings of this approach remain enignmatic, however. Using quantitative proteomics and RNA sequencing, we explore the molecular basis of attenuation in a strain of bacteriophage T7 whose major capsid gene was engineered to carry 182 suboptimal codons. As expected, there was no evident effect of the recoding on transcription. Proteomic observations revealed that translation is halved for the recoded major capsid gene, and a smaller reduction applies to a few genes downstream, potentially caused by translational coupling. Viral burst size is also approximately halved, and the fitness drop accompanying attenuation is compatible with the reduced burst size. Overall, the fitness effect and molecular basis of attenuation by codon deoptimization are compatible with a relatively simple model of reduced translation of a few genes and a consequent diminished virion assembly. This mechanism is simpler than that operating in eukaryotic viruses.

systems biology↗

bioRxiv2016

The E. coli molecular phenotype under different growth conditions

Modern systems biology requires extensive, carefully curated measurements of cellular components in response to different environmental conditions. While high-throughput methods have made transcriptomics and proteomics datasets widely accessible and relatively economical to generate, systematic measurements of both mRNA and protein abundances under a wide range of different conditions are still relatively rare. Here we present a detailed, genome-wide transcriptomics and proteomics dataset of E. coli grown under 34 different conditions. We manipulate concentrations of sodium and magnesium in the growth media, and we consider four different carbon sources glucose, gluconate, lactate, and glycerol. Moreover, samples are taken both in exponential and stationary phase, and we include two extensive time-courses, with multiple samples taken between 3 hours and 2 weeks. We find that exponential-phase samples systematically differ from stationary-phase samples, in particular at the level of mRNA. Regulatory responses to different carbon sources or salt stresses are more moderate, but we find numerous differentially expressed genes for growth on gluconate and under salt and magnesium stress. Our data set provides a rich resource for future computational modeling of E. coli gene regulation, transcription, and translation.

bioinformatics↗