Sip2 and Yeast Life Span
Researchers are foraging for longevity-related genes that have nothing to do with the known processes of life extension through calorie restriction: "We believe that for the first time, we have a biochemical route to youth and aging that has nothing to do with diet. ... The chemical variation, known as acetylation because it adds an acetyl group to an existing molecule, is a kind of 'decoration' that goes on and off a protein - in this case, the protein Sip2 - much like an ornament can be put on and taken off a Christmas tree ... Acetylation can profoundly change protein function in order to help an organism or system adapt quickly to its environment. Until now, acetylation had not been directly implicated in the aging pathway, so this is an all-new role and potential target for prevention or treatment strategies, the researchers say. The team showed that acetylation of the protein Sip2 affected longevity defined in terms of how many times a yeast cell can divide, or 'replicative life span.' The normal replicative lifespan in natural yeast is 25. In the yeast genetically modified by researchers to restore the chemical modification, life span extended to 38, an increase of about 50 percent. The researchers were able to manipulate the yeast life span by mutating certain chemical residues to mimic the acetylated and deacetylated forms of the protein Sip2. They worked with live yeast in a dish, measuring and comparing the life spans of natural and genetically altered types. ... When we give back this protein acetylation, we rescued the life span shortening in old cells. Our next task is to prove that this phenomenon also happens in mammalian cells."