X-Message-Number: 13262 From: Brent Thomas <> Subject: possible genetic intervention for ageing Date: Thu, 17 Feb 2000 09:45:07 -0500 taken from -- http://news.excite.com/news/r/000216/14/science-science-aging LONDON (Reuters) - U.S. scientists have uncovered new information about a gene in yeast that they think could one day be used to increase the lifespan of humans. The gene is called Silent Information Regulator, or SIR2. In yeast cells it controls longevity by silencing, or turning off, whole sections of the yeast genome. Leonard Guarente and scientists at the Massachusetts Institute of Technology (MIT) have discovered how SIR2 works and are trying to determine if it could extend the lives of animals and possibly humans. "It is a conserve gene. We have it, mice have it. It's ubiquitous. We know in yeast it can extend lifespan. We know it has this activity which connects metabolic rate to genome silencing and in yeast cells promotes longevity," Guarente said in a telephone interview Wednesday. "The connection between aging and metabolism rate is universal. For many years we've known that if you restrict calories you slow metabolic rate and the organism lives longer." In a report in the science journal Nature, the researchers described how they discovered that organisms such as yeast which have an extra copy of the SIR2 gene live longer. But if yeast has no SIR2 gene the cells' life span decreases. They also found that SIR2 needs another co-enzyme, called NAD, which is intimately associated with the metabolic rate of cells, to work. "We think it is a reasonable inference that SIR2 is coupled to NAD so that it senses the metabolic rate of cells and then decides how much silencing to impose," Guarente added. If NAD is too high it comes in and silences more. LIFESPAN INCREASED Previous studies have shown that the life spans of yeast, earthworms, mice and possibly primates can be extended by restricting calories to 70 percent of normal levels. The MIT researchers suspect that if an organism is starved for calories, the NAD level may go up. More NAD means activating SIR2, which silences sections of the genome and increases life span. As yeast cells age some of their genetic material falls off the chromosome and accumulates in the cell, eventually causing it to die. SIR2 seems to prevent this by silencing parts of the genome. The researchers said SIR2 is also probably involved in silencing mouse cells in response to metabolism. "If you give yeast more SIR2 genes they live longer. Will that be true in animals? That's the acid test. If it is true, it's exciting because it suggests we will be able to intervene in this (aging) process," he added. When the scientists gave the yeast one extra copy of the gene it extended their normal lifespan by about 40-50 percent. "All investigations led us to this gene," said Guarente. "If we can keep SIR2 active for longer, we may slow down aging." Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13262