Anita K. Hopper

Hopper made major contributions to our understanding of how tRNAs are processed and sorted in response to appropriate environmental cues. She identified the first eukaryotic mutants defective in RNA biogenesis, including numerous genes involved in RNA nuclear export such as, RNA1, the RanGAP, and LOS1, the tRNA nuclear exportin. Hopper discovered the first mechanisms of “sorting enzymes” – proteins encoded by single genes that are shared by mitochondrial and nuclear/cytoplasmic compartments. She discovered the paradigm-shifting tRNA retrograde transport pathway by which cytoplasmic tRNAs accumulate in the nucleus upon nutrient stress or tRNA damage. She discovered that this process functions in tRNA quality control and regulation of protein synthesis. Her recent genome-wide approaches led to the discovery of 142 novel gene products that function in tRNA biology, including a mechanism for tRNA intron turnover, gene products functioning in locating RNA processing enzymes to the mitochondrial surface, and multiple parallel pathways for tRNA nuclear/cytoplasmic bidirectional movement. Her studies have broad implications, because tRNA nuclear/cytoplasmic exchange pathways are regulated by nutrient availability and exhibit substrate specificity, suggesting that tRNA subcellular dynamics serves to regulate the proteome.