Retrograde nuclear accumulation of cytoplasmic tRNA in rat hepatoma cells in response to amino acid deprivation.
Until recently, transport of tRNA was presumed to be unidirectional, from the nucleus to the cytoplasm. Our published findings, however, revealed that cytoplasmic tRNAs move retrograde to the nucleus in Saccharomyces cerevisiae and that nuclear accumulation of cytoplasmic tRNAs occurs when cells are nutrient deprived. The findings led us to examine whether retrograde nuclear accumulation of cytoplasmic tRNAs occurs in higher eukaryotes. Using RNA FISH and Northern and Western analyses we show that tRNAs accumulate in nuclei of a hepatoma cell line in response to amino acid deprivation. To discern whether tRNA nuclear accumulation results from nuclear import of cytoplasmic tRNAs, transcription of new RNAs was inhibited, and the location of "old" tRNAs in response to nutrient stress was determined. Even in the absence of new RNA synthesis, there were significant tRNA nuclear pools after amino acid depletion, providing strong evidence that retrograde traffic is responsible for the tRNA nuclear pools. Further analyses showed that retrograde tRNA nuclear accumulation in hepatoma cells is a reversible and energy-dependent process. The data provide evidence for retrograde tRNA nuclear accumulation in intact mammalian cells and support the hypothesis that nuclear accumulation of cytoplasmic tRNA and tRNA re-export to the cytoplasm may constitute a universal mechanism for posttranscriptional regulation of global gene expression in response to nutrient availability.
Shaheen
Hussam H
HH
Department of Molecular Genetics, Ohio State University, 484 West 12th Avenue, Room Riffe 800, Columbus, OH 43210, USA.
Horetsky
Rick L
RL
Kimball
Scot R
SR
Murthi
Athulaprabha
A
Jefferson
Leonard S
LS
Hopper
Anita K
AK
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000596:Amino Acids / Q000172:deficiency* / Q000494:pharmacology; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D045744:Cell Line, Tumor / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D017404:In Situ Hybridization, Fluorescence; D012343:RNA, Transfer / Q000378:metabolism*; D051381:Rats
D000596:Amino Acids; D012343:RNA, Transfer