An international team of researchers reporting in the journal Current Biology has found evidence that ageing works through a special set of genes that everyone has – the rDNA genes.

“This work is exciting because it shows that rDNA instability is a new factor in ageing,” said study co-author Dr Austen Ganley from Massey University, New Zealand.

Dr Ganley and his colleagues from Japan found that by improving the stability of the rDNA genes they could extend the lifespan of the yeast Saccharomyces cerevisiae, a model system for studying cell ageing.

They set out to understand how the Sir2 gene reduces aging in Saccharomyces cerevisiae. Sir2 genes shot to prominence as potential human anti-aging 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-aging effect comes exclusively through stabilization 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 aging across life,” Dr Ganley said.

Senior author Dr Takehiko Kobayashi from the National Institute of Genetics in Mishima, Japan, originally proposed a role for rDNA instability in aging 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.

“The role of the rDNA genes in human aging still needs to be clarified,” Dr Ganley noted.

“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.”

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Bibliographic information: Kimiko Saka et al. Cellular Senescence in Yeast Is Regulated by rDNA Noncoding Transcription. Current Biology, published online August 29, 2013; doi: 10.1016/j.cub.2013.07.048