June 19, 2009
We are proud to announce the awarding of the Nissan Science Prize to Professor Fuyuki Ishikawa of the Graduate School of Biostudies of Kyoto University. This Prize is awarded by the Nissan Science Foundation to researchers who have made outstanding research achievements in fundamental research regarding the global environment, and who are expected to make further achievements. This occasion marks the 16th awarding of the prize, and Professor Ishikawa is the 30th recipient.
This Prize has been awarded in recognition of Professor Ishikawa's achievements in research on the telomere chromosome which determines cellular aging.
The award ceremony took place at the headquarters of Nissan Motor Company on June 18, 2009.
Research overview
DNA, the blueprint of all living organisms, is a chemical compound consisting of basic units called nucleotides connected in strand form. When cells divide, the DNA synthetic enzyme duplicates one strand of DNA, creating two identical strands, and each daughter cell receives one strand, ensuring the transmission of the blueprint to the descendents. Doctor Watson, renowned for discovering the double-helix structure of DNA, hypothesized in 1972 that the DNA synthetic enzyme was incapable of making a complete replication of the very ends of the stranded DNA, based on the identification of the reaction mechanism of the DNA synthetic enzyme by the early 1970s. This hypothesis became known as the "end-replication problem," and was later proven to actually occur within cells. In other words, when DNA is replicated upon cell division, the DNA is shortened, losing the end portion, known as the telomere. DNA shortening is one of the causes of cellular aging. When a cell repeatedly divides and the DNA is shortened to a certain length, the cell division stops, and the cell reaches the end of its life.
Living organisms are divided into eukaryotes, to which human beings belong, and prokaryotes including bacteria, such as Bacterium coli. All eukaryotes have stranded DNA, and with each cell division the “end-replication problem” causes the telomere shortening of the DNA, requiring a special mechanism to compensate for this shortening. On the other hand, prokaryotes have circular DNA, with no ends, which means the "end-replication problem" does not occur; therefore, there is no loss of DNA upon cell division. It was previously unknown why the DNA of eukaryotes and prokaryotes took different forms.
Professor Ishikawa succeeded for the first time in the world in creating a eukaryote with circular DNA, and discovered that such a eukaryote was incapable of sexual reproduction. Sexual reproduction is a phenomenon seen only in eukaryotes, and does not exist among prokaryotes. Moreover, it is believed that eukaryotes recombine the DNA to give slightly different DNA to each individual organism, providing complexity. From this, Professor Ishikawa concluded that eukaryotes had “accepted” the fate of cellular aging due to the end-replication problem, as a cost of gaining complex functions through sexual reproduction. This indicates that the different forms of DNA caused eukaryotes and prokaryotes, the two broad groups of living organisms, to evolve in completely different directions.
Aside from this achievement, Professor Ishikawa is highly regarded worldwide for his many pioneering research activities regarding fundamental research on the enzyme telomerase, one of the substances used to resolve the end-replication problem. These research achievements are expected to aid the prevention and treatment of malignant cell alteration and aging.
Summary of achievements
Succeeded in creating yeast with circular DNA and discovered a major reason why organisms evolved into diverse species. Also, through research on telomere, explained the mechanisms of cellular aging as well as the proliferation of cancer cells.
- Succeeded in creating a yeast (a eukaryote) with circular DNA, and discovered it was incapable of sexual reproduction. Eukaryotes have stranded DNA, and even though telomere on the ends results in cellular aging, this allows sexual reproduction, resulting in a diversity of organisms.
- Succeeded in detecting telomerase activity, which can resolve telomere shortening, in human cells. Also, revealed the mechanism in which, while there is no telomerase activity in normal cells, enabling cellular aging to occur, there is high activity in cancer cells which allows infinite proliferation.
- Succeeded in identifying telomeric components.