Inorganic phosphate deprivation causes tRNA nuclear accumulation via retrograde transport in Saccharomyces cerevisiae

Nuclear export of IRNA is an essential eukaryotic function, yet the one known yeast tRNA nuclear exporter, Los1, is nonessential. Moreover recent Studies have shown that tRNAs can move retrograde from tile cytosol to the nucleus by an undefined process. Therefore, additional gene products involved in tRNA nuleus-cytosol dynamics have yet to be identified. Synthetic genetic array (SGA) analysis was employed to identify proteins involved in Los1-independent tRNA transport and in regulating IRNA nucleus-cytosol distribution. These studies uncovered synthetic interactions between los1 Delta and pho88 Delta involved in inorganic phopshate uptake. Further analysis revealed that inorganic phosphate deprivation causes transient, temperature-dependent nuclear accumulation of mature cytoplasmic tRNA within nuclei via a Mtr10- and retrograde-dependent pathway, providing a novel connection between tRNA subcellular dynamics and phosphate availability.