Effects of mirror-image nucleosides on DNA replication and transcription in human cells

Mirror-image nucleosides, as potential antiviral drugs, can inhibit virus DNA polymerase to prevent virus replication. Conversely, they may be inserted into the DNA strands during DNA replication or transcription processes, leading to mutations that affect genome stability. Accumulation of significant mutation damage in cells may result in cell aging, apoptosis, and even uncontrolled cell division. We have previously explored replicative repair of mirror-image nucleosides within Escherichia coli, and this study focuses on human cells. We constructed several plasmid substrates, each carrying a specific mirror-image nucleoside, to investigate their impact on intracellular DNA replication and transcription processes. The results showed that in HepG2 cells, L-adenosine (L-dA) was the most potent substrate in inhibiting cell replication and transcription. L-cytidine (L-dC) exhibited the highest bypass efficiency in both template and non-template strands and had the most diverse mutation types. We also observed that L-dC induced immunoregulation of the JAK-STAT signaling pathway. Therefore, our results provide a theoretical basis for the disruptions caused by mirror-image nucleosides in replication and transcription and give us some understanding that mirror-image nucleoside drugs can cause cytotoxicity.