Ribosome Collision-Reducing ac4C Modification Technology Enhances the Accuracy of Next-Generation mRNA Vaccines
Background
Following the success of the Pfizer and Moderna COVID-19 vaccines, mRNA platforms have become a mainstay of modern medicine. This technology utilizes in vitro transcription (IVT) to deliver genetic information directly into cells, inducing the expression of target proteins. However, synthetic mRNA introduced from external sources is readily degraded by immune cells or can trigger dangerous inflammatory responses. To overcome this, researchers have explored modifying uracil bases to N1-methylpseudouridine (m1Ψ). The introduction of m1Ψ has significantly contributed to evading innate immune sensors, increasing the stability of synthetic mRNA, and enhancing protein production.
However, this standard technology still presents unresolved molecular biological challenges. When ribosomes translate mRNA codons, a delay in translation speed is observed in the m1Ψ-modified region. A slower translation elongation rate not only reduces protein synthesis efficiency but also leads to ribosome collisions as ribosomes accumulate. When ribosomes collide, the cell's quality control system is activated, which can forcibly stop translation or cause frameshift errors, leading to the production of abnormal proteins. These protein synthesis defects remain a hurdle in improving the stability of existing mRNA vaccine platforms.
Key Findings
To address this issue, the research team focused on N4-acetylcytidine (ac4C) modification, a natural RNA modification. ac4C is a naturally occurring RNA modification found in eukaryotic genomes and functions to fine-tune the translational elongation stage of ribosomes. The researchers designed IVT mRNA models with various modified bases and conducted experiments to directly compare translation efficiency and accuracy.
The results showed that synthetic mRNA containing ac4C exhibited an average of two times faster translation elongation rates compared to the industry standard m1Ψ-based mRNA. Due to the faster translation speed, ribosomes smoothly traversed the sequence without bottlenecks, significantly reducing cellular stress responses associated with ribosome collision signals. Most notably, translation fidelity was dramatically improved. The frequency of +1 ribosomal frameshifting, frequently observed in m1Ψ codon structures, was significantly reduced to levels comparable to unmodified mRNA in the ac4C environment. This indicates that the ribosome accurately reads the three-nucleotide codon units, precisely decoding only the intended antigen genetic information.
Significance and Prospects
This research has the potential to fundamentally change the paradigm of designing therapeutic genetic materials. By presenting ac4C as an alternative in the mRNA modification field, which has been dominated by m1Ψ, it has enabled the design of safer and more reliable next-generation therapeutics. In particular, the value of ac4C is expected to be even more prominent in the area of chronic disease treatments and cancer vaccines, which require the continuous synthesis of highly precise proteins with a single administration. This is because it eliminates concerns about immune adverse reactions caused by the production of defective proteins.
However, there are several hurdles to overcome before ac4C-modified mRNA can be fully implemented in clinical and production settings. The control technology for uniformly inserting ac4C at the desired location in the currently developed in vitro synthesis process needs to be further refined. In addition, research on the standardization of purification protocols to ensure uniform quality in commercial large-scale production has already begun. In the future, additional long-term toxicity and safety data in various animal models will also be essential for commercialization.
Nature, Published online: 01 July 2026; doi:10.1038/s41586-026-10729-8Different RNA modifications elicit different translation elongation rates for in vitro transcribed mRNAs that result in disparate translation outputs and fidelity, as shown here for N4-acetylcytidine versus the industry standard for synthetic mRNAs, N1-methylpseudouridine.
Consider a scenario in which a patient-specific cancer vaccine is administered in a clinical setting; the value of ac4C modification becomes even clearer. When producing an mRNA vaccine containing neoantigen information extracted from the patient's tumor cells, translation accuracy is key to the vaccine's efficacy. If frameshifting occurs during intracellular translation, unintended proteins will be produced. This can induce unexpected autoimmune reactions or reduce the ability to target cancer cells.
By introducing the ac4C platform, this type of translation error can be prevented, ensuring safety after administration and precisely inducing only the desired immune response. From a pharmaceutical industry perspective, high translation accuracy and speed will also provide direct benefits, such as reducing production costs and mitigating adverse effects by reducing the effective drug dose.