Dynamic shuttling of TIA-1 accompanies the recruitment of mRNA to mammalian stress granules.
Mammalian stress granules (SGs) harbor untranslated mRNAs that accumulate in cells exposed to environmental stress. Drugs that stabilize polysomes (emetine) inhibit the assembly of SGs, whereas drugs that destabilize polysomes (puromycin) promote the assembly of SGs. Moreover, emetine dissolves preformed SGs as it promotes the assembly of polysomes, suggesting that these mRNP species (i.e., SGs and polysomes) exist in equilibrium. We used green flourescent protein-tagged SG-associated RNA-binding proteins (specifically, TIA-1 and poly[A] binding protein [PABP-I]) to monitor SG assembly, disassembly, and turnover in live cells. Fluorescence recovery after photobleaching shows that both TIA-1 and PABP-I rapidly and continuously shuttle in and out of SGs, indicating that the assembly of SGs is a highly dynamic process. This unexpected result leads us to propose that mammalian SGs are sites at which untranslated mRNAs are sorted and processed for either reinitiation, degradation, or packaging into stable nonpolysomal mRNP complexes. A truncation mutant of TIA-1 (TIA-1DeltaRRM), which acts as a transdominant inhibitor of SG assembly, promotes the expression of cotransfected reporter genes in COS transfectants, suggesting that this process of mRNA triage might, directly or indirectly, influence protein expression.
Kedersha
N
N
Division of Rheumatology and Immunology, Harvard Medical School, Hematology Division, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Cho
M R
MR
Li
W
W
Yacono
P W
PW
Chen
S
S
Gilks
N
N
Golan
D E
DE
Anderson
P
P
D000818:Animals; D019556:COS Cells; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004640:Emetine / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D039102:Poly(A)-Binding Proteins; D011132:Polyribosomes / Q000378:metabolism; D011471:Prostatic Neoplasms; D014176:Protein Biosynthesis; D011506:Proteins; D011691:Puromycin / Q000494:pharmacology; D023121:RNA, Messenger, Stored / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D013312:Stress, Physiological / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D008565:Membrane Proteins; D039102:Poly(A)-Binding Proteins; D011506:Proteins; D023121:RNA, Messenger, Stored; D016601:RNA-Binding Proteins; D011691:Puromycin; D004640:Emetine