Caloric restriction and life span determination of yeast cells.

The diet known as caloric restriction (CR) has been known for 70 yr to extend the life span of rodents (1). CR can also extend life span in a broad range of other species as well, from unicellular organisms (2,3), to invertebrates (4) and most likely primates, as well (5). The budding yeast Saccharomyces cerevisiae is a useful model for the study of pathways that determine life span in response to dietary intake. Here, we describe how to calorically restrict yeast, the methods used to determine the replicative life span of single yeast "mother" cells and measure recombination frequency at the rDNA locus, and how to isolate and analyze the circular forms of DNA known as extrachromosomal rDNA circles (ERCs), which are a major cause of aging in S. cerevisiae (6-8).