In Situ Visualizing the Recognition Between Proteins and Platinum-Damaged DNA in Single-Cells by Correlated Optical and Secondary Ion Mass Spectrometric Imaging

In situ visualization of the recognition and interactions between proteins and drug damaged DNA at single cell level is highly important for understanding the molecular mechanism of action of DNA targeting drugs, yet a great challenge. We report herein a novel approach, termed as correlated optical and secondary ion mass spectrometric imaging (COSIMSi), to explore the recognition between proteins and cisplatin-damaged DNA in single cells. Genetically encoded EYFP-fused HMGB1, an in vitro well-known specific binder of cisplatin-damaged DNA, dye-stained DNA, and platinum were mapped by LSCM and ToF-SIMS imaging, respectively. The LSCM and SIMS images were aligned with aiding of an addressable silicon wafer to generate fused images, in which the co-localization of the fluorescent and MS signals indicated the formation of HMGB1-Pt-DNA ternary complexes in a dose- and time-dependent manner. In contrast, COSIMSi results showed that little HMGB1(F37A)-Pt-DNA complex was produced under the same conditions. Moreover, we demonstrated for the first time that cisplatin lesions on DNA prevented DNA-binding proteins Smad3 and Smad7 from interacting with DNA. These results verify that the COSIMSi is an effective and straightforward tool for in situ visualization of recognition and interactions between proteins and specific damaged DNA in single cells.