Overcoming the eIF2α Brake in Human Cell-Derived Translation Systems

Area of Science:

• Molecular Biology
• Cell Biology
• Synthetic Biology

Background:

• Cell-free translation systems derived from human cells are crucial for studying gene expression and developing synthetic biology tools.
• Productivity in these systems is often limited by the inhibitory phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α) at the Ser52 residue.

Purpose of the Study:

• To systematically explore and compare strategies for bypassing the eIF2α phosphorylation-mediated initiation block in both editable and hard-to-edit human cell types.
• To identify optimal methods for generating high-activity human cell-free translation extracts.

Main Methods:

• Genome editing of EIF2S1 to create an eIF2α-S52A mutant in Expi293F cells.
• Genetic knockout of EIF2AK2 (PKR) in Expi293F cells.
• Stable piggyBac integration of truncated GADD34 (PPP1R15A) and K3L under Tet-inducible control in iPSCs and primary fibroblasts.
• Differentiation of engineered iPSCs into cardiomyocytes for extract production.

Main Results:

• Genome editing to block eIF2α Ser52 phosphorylation (eIF2α-S52A) in Expi293F cells significantly increased translation extract activity.
• Knockout of EIF2AK2 (PKR) also enhanced translation in Expi293F lysates, confirming eIF2α phosphorylation as a key bottleneck.
• Expression of GADD34 and K3L via piggyBac system in iPSCs (including cardiomyocytes) and primary fibroblasts successfully improved translation output.
• These expression-based methods provide a viable alternative for systems where genome editing is not feasible.

Conclusions:

• eIF2α phosphorylation is a primary barrier to robust translation in human cell-free extracts.
• Genome editing of eIF2α or PKR knockout are optimal for editable cell systems.
• A portable GADD34/K3L expression cassette enables the production of translationally active lysates from challenging or non-editable systems, broadening the utility of human cell-free translation.