Preparation of Tunable Microchips to Visualize Native Protein Complexes for Single-Particle Electron Microscopy

High-Resolution Imaging of Human Cancer Proteins Using Microprocessor Materials

Mutations in tumor suppressor genes, such as Tumor Protein 53 (TP53), are heavily implicated in aggressive cancers giving rise to gain- and loss-of-function phenotypes. While individual domains of the p53 protein have been studied extensively, structural information for full-length p53 remains incomplete. Functionalized microprocessor chips (microchips) with properties amenable to electron microscopy permitted us to visualize complete p53 assemblies for the first time. The new structures revealed p53 in an inactive dimeric state independent of DNA binding. Residues located at the protein-protein interface corresponded with modification sites in cancer-related hot spots. Changes in these regions may amplify the toxic effects of clinical mutations. Taken together, these results contribute advances in technology and imaging approaches to decode native protein models in different states of activation.

Microchip-Based Structure Determination of Disease-Relevant p53

The tumor suppressor protein TP53 (p53) plays a multifaceted role in all cells of the human body. Mutations in the TP53 gene are often involved in cancer induction and disease progression. Despite its important role in health and development, structural information for p53 remains incomplete. Here, we present a microchip-based technology to facilitate structural studies of p53 assemblies derived from human cancer cells. These devices do not introduce foreign sequences to the p53 gene and maintain naturally occurring post-translational modifications. Using cryo-electron microscopy, structures for the p53 monomer (∼50 kDa) and tetramer (∼200 kDa) were resolved to ∼4.8 and ∼7 Å, respectively. These structures revealed new insights for flexible regions of p53 along with biologically relevant ubiquitination sites. Collectively, the convergence of nanotechnology tools and structural imaging builds a strong framework to understand the oncogenic impact of p53 in human tissues.

Cryo-EM-On-a-Chip: Custom-Designed Substrates for the 3D Analysis of Macromolecules

The fight against human disease requires a multidisciplinary scientific approach. Applying tools from seemingly unrelated areas, such as materials science and molecular biology, researchers can overcome long-standing challenges to improve knowledge of molecular pathologies. Here, custom-designed substrates composed of silicon nitride (SiN) are used to study the 3D attributes of tumor suppressor proteins that function in DNA repair events. New on-chip preparation strategies enable the isolation of native protein complexes from human cancer cells. Combined techniques of cryo-electron microscopy (EM) and molecular modeling reveal a new modified form of the p53 tumor suppressor present in aggressive glioblastoma multiforme cancer cells. Taken together, the findings provide a radical new design for cryo-EM substrates to evaluate the structures of disease-related macromolecules.