Project description:Genetically encoded unnatural amino acids provide powerful strategies for modulating the molecular functions of proteins in mammalian cells. However this approach has not been coupled to genome-wide measurements, because efficient unnatural amino acid incorporation is limited to readily transfectable cells and leads to very heterogeneous expression. We demonstrate that rapid piggybac integration of the orthogonal pyrrolysyl-tRNA synthetase (PylS)/tRNAPyl CUA pair (and its derivatives) into the mammalian genome enables efficient, homogeneous unnatural amino acid incorporation into target proteins in diverse cells, and we reveal the distinct transcriptional responses of ES cells and MEFs to amber suppression. Genetically encoding Nε-acetyl-lysine in place of six lysine residues in histone H3, that are known to be post-translationally acetylated, enables deposition of pre-acetylated histones into cellular chromatin, via a synthetic pathway that is orthogonal to enzymatic modification, allowing us to determine the consequences of acetylation at specific amino acids in histones on gene expression. mRNA was sequenced using polyA-enrichment and Truseq library preparation protocol. Two biological replicates were sequences for each cell line and condition
Project description:Genetically encoded unnatural amino acids provide powerful strategies for modulating the molecular functions of proteins in mammalian cells. However this approach has not been coupled to genome-wide measurements, because efficient unnatural amino acid incorporation is limited to readily transfectable cells and leads to very heterogeneous expression. We demonstrate that rapid piggybac integration of the orthogonal pyrrolysyl-tRNA synthetase (PylS)/tRNAPyl CUA pair (and its derivatives) into the mammalian genome enables efficient, homogeneous unnatural amino acid incorporation into target proteins in diverse cells, and we reveal the distinct transcriptional responses of ES cells and MEFs to amber suppression. Genetically encoding Nε-acetyl-lysine in place of six lysine residues in histone H3, that are known to be post-translationally acetylated, enables deposition of pre-acetylated histones into cellular chromatin, via a synthetic pathway that is orthogonal to enzymatic modification, allowing us to determine the consequences of acetylation at specific amino acids in histones on gene expression.
Project description:An orthogonal aminoacyl-tRNA synthetase/tRNA pair is a key prerequisite for site-specific incorporation of unnatural amino acids. Due to its high codon suppression efficiency and full orthogonality, the pyrrolysyl-tRNA synthetase/pyrrolysyl-tRNA pair is currently the ideal system for genetic code expansion in both eukaryotes and prokaryotes. There is a pressing need to discover or engineer other fully orthogonal translation systems that allow unnatural amino acids with distinct scaffolds and functionalities to be incorporated into a wide range of living organisms efficiently. Here, through rational chimera design by transplanting the key orthogonal components from the pyrrolysine system, we create multiple chimeric tRNA synthetase/chimeric tRNA pairs, including chimera histidine, phenylalanine, and alanine systems. We further show that these engineered chimeric systems are orthogonal and highly efficient with comparable flexibility to the pyrrolysine system. In addition, the chimera phenylalanine system can incorporate a group of phenylalanine, tyrosine and tryptophan analogues efficiently in both E. coli and mammalian cells. These aromatic amino acids analogous exhibit unique properties and characteristics, including fluorescence, post-translation modification. To our knowledge, most of these molecules have never been shown to be incorporated with fully orthogonal pairs. Therefore, these chimera pairs offer the potential for incorporation of de novo unnatural amino acids into target proteins for a variety of applications.
Project description:Synthetic biology holds immense promise to tackle key problems we are facing, for instance in resource use, environmental health, and human health care. However, comprehensive safety measures are needed to deploy genetically engineered microorganisms in open-environment applications. Intrinsic, genetically encoded biocontainment systems, which control cell survival based on environmental cues, can solve this issue. Here, we describe a genetic biocontainment system based on conditional stability of essential proteins. We used a yeast-adapted destabilizing domain degron, which can be stabilized by estradiol addition (ERdd). Leveraging the yeast GFP collection and lab automation platforms, we ERdd-tagged 775 essential genes and screened for strains with estradiol dependent growth. Three genes, SPC110, DIS3 and RRP46, were found to be particularly suitable targets. Respective strains showed no growth defect in the presence of estradiol and strong growth inhibition in its absence. SPC110-ERdd offered the most stringent containment, with an escape frequency of 7.0x10-8, and full growth restoration at 100 nM estradiol. By systematically analyzing the containment escapees, we identified the non-essential C-terminal region of SPC110 as target for escape mutations. Its removal decreased the escape frequency with a single ERdd tag further to 4.9x10-9. Combining SPC110-ERdd with a second ERdd tag on either DIS3 or RRP46 resulted in escape frequencies below the detection limit of the used assay (<2x10-10). Being based on conditional protein stability, this approach is mechanistically orthogonal to previously reported intrinsic biocontainment systems. It thus can be readily combined with other systems, for instance ones based on transcriptional or translational control of essential gene expression, to achieve multiplexed, extremely stringent control over the survival of engineered organisms.