DNA is responsible for the transmission of genetic information and is also an attractive research subject from the viewpoint of its chemical structure and function. Dr. Sugiyama is pursuing unique comprehensive research on the structure and functional control of DNA by actively incorporating the latest biological organic chemistry and molecular biology techniques and has become a pioneer in researching the chemistry of DNA. Using fast atomic force microscopy (AFM) to visualize the single-molecule dynamics of DNA, Dr. Sugiyama has played an important role in the rapidly growing field of DNA nanobiotechnology. Internationally, he is recognized as a pioneering researcher of the structure and function of DNA. Following is a summary of his many achievements.
1. Development of a genetic switch for the on-off expression of specific genes
To produce a genetic switch that turns on specific gene expression, Dr. Sugiyama developed a histone deacetylase (HDAC) inhibitor conjugated to pyrrole-imidazole (Py-Im) polyamide that has remarkable properties such as sequence-specific DNA binding, effects on cell permeability, and nuclear localization. He has constructed a library of 32 types of Py-Im polyamide conjugates that bind to different base sequences and has evaluated gene expression using DNA microarray technology in mice and human cells. Dr. Sugiyama contributed to the discovery that upregulation of gene expression in different transcriptional networks is based on sequence specificity. To develop a genetic switch that turns off specific gene expression, Dr. Sugiyama synthesized a functional Py-Im polyamide with a DNA alkylating agent. His research group found that the functional polyamide targets the mutant (GTT) sequence of Kras codon 12, which is found in colorectal cancer and pancreatic cancer where it effectively suppresses Kras expression. They confirmed the compound's effectiveness in experiments using human colorectal cancer cells and tumor-bearing mice. Dr. Sugiyama's research team has also successfully developed functional polyamides that inhibit the binding of RUNX family genes, which are among the key transcription factors responsible for tumor growth and are drug candidates for the treatment of leukemia, lung cancer, and stomach cancer.
2. Development of functional Py-Im polyamides that recognize human telomeric sequences
Based on the sequence-specific DNA binding properties of Py-Im polyamide, Dr. Sugiyama has developed a fluorescent Py-Im polyamide that binds specifically to the telomere region at the end of chromosomes. To improve its specificity for human telomeric sequences, they developed a new method for synthesizing a tandem type of Py-Im polyamide in which two hairpin Py-Im polyamides are linked. By introducing newly developed block parts into solid-phase synthesis, this method contributes greatly to the efficient synthesis of tandem Py-Im polyamides. Development of this synthetic method made it possible to synthesize a tandem tetramer that recognizes a maximum of 24 base pairs, as judged by next-generation sequencing technology. Using this fluorescent Py-Im polyamide, Dr. Sugiyama's research team have successfully visualized the intracellular telomere region in the double-stranded state under a confocal microscope.
3. Development of visualization technology to observe the dynamics of single molecules using the DNA origami method and high-speed AFM
Using the DNA origami method, we have developed a nanostructure called a "DNA frame," which has a nanoscale space (40×40 nm), and we have analyzed the enzymatic reactions and structural changes in DNA using high-speed AFM. In the nanospace of this DNA frame, it is possible to arbitrarily control the arrangement, tension, and direction of the substrate DNA chain. In reactions requiring DNA conformational changes induced by proteins, such as DNA methylation and DNA repair, the efficiency of the reaction is modulated by the tension of the double stranded DNA. Dr. Sugiyama's group has demonstrated that the orientation of DNA substrates is important to the DNA recombination reaction. This platform has been applied to demonstrate that, by binding and cleaving the core of Holliday junctions symmetrically, the enzyme MOC1 is necessary for the segregation of chloroplasts. Recently, we have also created nanostructures called "nanocages" using the DNA origami method. Analysis using optical tweezer technology confirmed that the guanine quadruplex structure contained inside the nanocage is subjected to a large stabilization contribution.
4. Development of a programmable supramolecular system based on the DNA origami structure
High-speed AFM has been used to visualize the motion of a "DNA motor" constructed using the DNA origami method and its stepwise movement. We have succeeded in creating branching paths into multiple on DNA origami and in selecting specific pathways according to the program determined by the base sequence. We have also established a supramolecular system that can programmatically arrange DNA nanostructures in one and two dimensions, similar to a jigsaw puzzle, by adapting the base sequence and shape. In particular, when observing the self-assembly of DNA nanostructures on a lipid bilayer and the assembly-dissociation of hexagonal nanostructures comprising photoresponsive DNA chains, we have visualized the formation of two-dimensional crystals of periodical lattice structure.
As highlighted above, Dr. Sugiyama has established a wide-ranging research program based on his original ideas in the field of biofunction-related chemistry and biotechnology. His achievements have had a great influence on this and other research fields. Therefore, in recognition of his achievements, Dr. Sugiyama is clearly a worthy recipient of the Japan Chemical Society Award.