Mammals feed off yeast pathway

The biochemical pathway that senses amino acid deficiencies in yeast is also at work in mammals, researchers report in this week's Science. While this signaling initiates amino acid synthesis in yeast, it alters eating behavior in rats, according to senior author Dorothy Gietzen of the University of California, Davis.

"What's most striking to me, because I'm a yeast geneticist, is that you'd be able to see this effect on feeding behavior," Alan Hinnebusch of the National Institutes of Health, who was not involved in the study, told The Scientist.

In yeast, a deficiency of a particular amino acid causes an accumulation of that amino acid's corresponding transfer RNA. This free tRNA—called "uncharged" because it is not attached to an amino acid—activates the kinase GC nonderepressing 2 (GCN2), which then phosphorylates eukaryotic initiation factor 2α (eIF-2α). This signal decreases the yeast's global protein synthesis and increases transcription of genes that synthesize ...