for National Geographic News
Scientists have discovered a means to extend the life span of yeast cells tenfold—and they say further research on unusual communities in Ecuador might offer hope for humans too.
The researchers achieved the feat by deleting two genes—SCH9 and RAS2—from baker's yeast and then subjecting the yeast cells to extreme starvation by restricting their calorie intake.
"Both these genes control cellular function and normally promote cell division and cell growth," said study leader Valter Longo, a biogerontologist at the University of Southern California in Los Angeles. "They are very similar to two of the main cancer-causing genes in humans."
But removing the genes alone does not do the trick. Increased life span in yeast appears to be linked to calorie restriction as well.
Such restriction reduces the activation of those genes, in turn activating an enzyme called Rim 15, Longo said.
(Related: "Long Life Span in Flies Reversed By Just Whiff of Food" [February 1, 2007].)
"[Rim15] triggers a number of proteins that comprise stress-protective systems in yeast cells," he added.
These proteins control antioxidant and DNA-repair enzymes and regulate the proper folding of proteins, which may explain the dramatic increase in yeast longevity.
But exactly how many of these proteins go about their jobs is still unclear.
"There are probably hundreds of genes which play different roles that are part of this switch from 'growth' mode to 'protective' mode. We're looking for them right now," said Longo, whose findings appeared in recent issues of PLoS Genetics and the Journal of Cell Biology.
Other researchers had previously identified genetic mutations in mice that reduced the amount of growth hormone produced. This increased the animals' life span by 50 percent and conferred protection against several diseases.
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