Nucleocytoplasmic shuttling of tRNAs and implication of the cytosolic Hsp70 system in tRNA import.
tRNAs, a class of non-coding RNAs essential for translation, are unique among cytosolic RNA species in that they shuttle between the nucleus and cytoplasm during their life. Although their export from the nucleus has been studied in detail, limited information on import machinery was available. Our group recently reported that Ssa2p, one of major cytosolic Hsp70s in Saccharomyces cerevisiae, acts as a crucial factor for tRNA import upon nutrient starvation. Ssa2p can bind tRNAs and a nucleoporin directly in an ATP-sensitive manner, suggesting that it acts as a nuclear import carrier for tRNAs, like importin-β proteins. In vitro assays revealed that Ssa2p binds tRNA specifically but has preference for loosely folded tRNAs. In this Extra View, these features of Ssa2p as a new import factor is discussed with other recent findings related to nucleocytoplasmic transport of tRNAs reported from other groups.
a Graduate School of Life Science; University of Hyogo ; Ako-gun , Hyogo , Japan.
Tohru
T
Yoshihisa
D015966:Gene Expression Regulation, Fungal; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D029701:Saccharomyces cerevisiae Proteins; D012343:RNA, Transfer
Hsp70; SSA2; nuclear import; starvation; tRNA; transport carrier; yeast