Melbourne: Imagine taking a drug that can reduce the rate at which you age, it may soon be a reality! A new study provides evidence that ageing works through a special set of genes that everyone has - the rDNA genes. The international team led by Dr Takehiko Kobayashi from the National Institute of Genetics in Mishima, Japan, found that by improving the stability of the rDNA genes, which are usually quite unstable, they could extend the lifespan of baker's yeast, a model system for studying cell ageing.
"This work is exciting because it shows that rDNA instability is a new factor in ageing," said Massey University senior lecturer in genetics Dr Austen Ganley. Researchers set out to understand how the Sir2 gene reduces aging in yeast. Sir2 genes shot to prominence as potential human anti-ageing genes with the finding that resveratrol, a component of red wine, activates them. However, subsequent research has found that resveratrol doesn't extend lifespan in mammals. The yeast Sir2 gene controls rDNA stability, but also has many other targets in the cell. The breakthrough came when the scientists found a way to separate Sir2's effect on the rDNA from its other effects. This allowed them to show that Sir2's anti-ageing effect comes exclusively through stabilisation of the rDNA genes.
"This is significant, because in humans there are seven Sirtuins (the equivalent of the Sir2 gene), and they all behave very differently to the yeast Sir2 gene. In contrast, the rDNA genes are very similar between yeast and humans, therefore rDNA gene instability may be the common factor in ageing across life," said Ganley. Kobayashi originally proposed a role for rDNA instability in ageing five years ago, but unequivocal support for this theory has been lacking until now. These new results suggest that finding a way to artificially improve rDNA gene stability may delay the ageing process in humans too.
However, Ganley cautions that the role of the rDNA genes in human ageing still needs to be clarified. "Although we know human rDNA genes are unstable, we don't know if this instability affects lifespan. Finding this out is the next critical step, and the challenge lies in doing these experiments with human cells, which are more difficult to work with than yeast," said Ganley. The study was published in the journal Current Biology.
