MedicalResearch.com Interview with:
Carlos E. Crespo-Hernández PhD
Associate Professor and Co-director of the Center for Chemical Dynamics
Department of Chemistry
Case Western Reserve University
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Two new letters of DNA have recently been successfully incorporated and replicated by a modified strain of E. coli, thus generating the world’s first semi-synthetic organism with an expanded genetic alphabet. With the expansion of the genetic alphabet, the question arises as to whether the incorporation of unnatural DNA base pairs into cells can adversely affect the integrity of the genetic code and the viability of the cells upon exposure to sunlight or even conventional laboratory lighting. Natural DNA is susceptible to damage by ultraviolet light, but this damage is largely repaired by enzymatic repair mechanisms in living cells. Our recent study has found that the two new, unnatural DNA bases—d5SICS and dNaM—are able to efficiently absorb near-visible light, which is abundant in sunlight and standard fluorescent lighting. Not only that, but upon absorbing near-visible light these unnatural bases produce up to 100 times more reactive species than the most reactive natural DNA base. A line of skin cancer cells incorporating one of these unnatural DNA bases was used to investigate these effects on living cells. Following exposure to a low dose of near-visible light, we observed an increase in the generation of reactive oxygen species within cells containing the unnatural DNA base and a significant decrease in cell survival.