Clues to long life may be hidden in human DNA
Scientists have taken a step forward in their efforts to discover the secrets behind a long life.
Researchers in the United States have identified a gene in yeast that influences how long it lives.
They believe the finding could boost efforts to identify similar genes in humans.
Yeast and humans share many genes. As a result, genes in yeast can often explain how human genes work.
Dr David Sinclair and colleagues at Harvard Medical School in Boston have found that a gene called PNC1 plays a key role in influencing the lifespan of yeast.
They have discovered that yeast with five copies of this gene can live up to 70% longer than normal yeast.
This is because the gene regulates the production of nicotinamide - a form of vitamin B3.
The researchers have previously shown that low levels of nicotinamide enable cells to live longer while high levels can cause cells to die faster.
In their latest study, the researchers found that yeast with additional copies of PNC1 produces less nicotinamide, increasing lifespan.
But they also found that the gene is sensitive to other factors, such as calorie restriction, heat and low salt levels.
Previous studies have suggested that severe calorie restriction can increase the lifespan of organisms like yeast, fruit flies, worms and rats. However, scientists have struggled to explain why.
The Harvard researchers believe that these factors influence PNC1 levels increasing them when necessary to prolong the life of cells.
This, they say, allows an organism such as yeast to change its survival strategies according to the environmental factors it faces.
Writing in the journal Nature, they said: "Lifespan extension from calories restriction is the result of an active cellular defence."
The findings could offer scientists clues to extending lifespan in humans.
The Harvard Medical School researchers are now investigating human genes that may play the same role as PNC1.