Terminal Deoxynucleotidyl Transferase Acts As a Signal Sensor and Writer for Biorecording and Data Storage Applications

DNA-based recording tools used for data archiving and investigating biological systems have significantly advanced the field of synthetic biology and enriched the bioeconomy. Like traditional electronic recording systems, state-of-the-art DNA-based recording systems consist of multiple components: a signal sensing, a signal transforming and a signal writing device. This multi-device architecture makes their recording characteristics intrinsically dependent on speed of each of those devices. The ideal DNA-based recorder would consist of a single device that could sense, transform and write into DNA with high accuracy and information density. We introduce terminal deoxynucleotidyl transferase (TdT) as both the signal sensor and writer, for biorecording and data storage applications. TdT, a template-independent DNA polymerase, upon interacting with the signal of interest alters its dNTP incorporation preference. The resulting single stranded DNA (ssDNA) synthesized thus functions as a molecular ticker tape. We show that in vitro, TdT can record various physiologically relevant signals like Co²⁺, Ca²⁺, Zn²⁺ concentrationsand temperature changes. Further, we record a single step change in Co²⁺ signal to within two minutes over a 60-minute period and record the rise and fall of an Co²⁺ input signal to within three minutes. Finally, we demonstrate a proof-of-concept for the TdT-based recording system in mammalian cell lines by writing “Hello World!” into the genomic DNA without the need of any externally synthesized oligonucleotides. We have thus expanded the repertoire of DNA-based recording techniques by developing a “DNA-synthesis” based system, that can record temporal environmental signals into DNA.