Translational control of cytochrome c by RNA-binding proteins TIA-1 and HuR.
Stresses affecting the endoplasmic reticulum (ER) globally modulate gene expression patterns by altering posttranscriptional processes such as translation. Here, we use tunicamycin (Tn) to investigate ER stress-triggered changes in the translation of cytochrome c, a pivotal regulator of apoptosis. We identified two RNA-binding proteins that associate with its approximately 900-bp-long, adenine- and uridine-rich 3' untranslated region (UTR): HuR, which displayed affinity for several regions of the cytochrome c 3'UTR, and T-cell-restricted intracellular antigen 1 (TIA-1), which preferentially bound the segment proximal to the coding region. HuR did not appear to influence the cytochrome c mRNA levels but instead promoted cytochrome c translation, as HuR silencing greatly diminished the levels of nascent cytochrome c protein. By contrast, TIA-1 functioned as a translational repressor of cytochrome c, with interventions to silence TIA-1 dramatically increasing cytochrome c translation. Following treatment with Tn, HuR binding to cytochrome c mRNA decreased, and both the presence of cytochrome c mRNA within actively translating polysomes and the rate of cytochrome c translation declined. Taken together, our data suggest that the translation rate of cytochrome c is determined by the opposing influences of HuR and TIA-1 upon the cytochrome c mRNA. Under unstressed conditions, cytochrome c mRNA is actively translated, but in response to ER stress agents, both HuR and TIA-1 contribute to lowering its biosynthesis rate. We propose that HuR and TIA-1 function coordinately to maintain precise levels of cytochrome c production under unstimulated conditions and to modify cytochrome c translation when damaged cells are faced with molecular decisions to follow a prosurvival or a prodeath path.
Laboratory of Cellular and Molecular Biology, National Institute on Aging-Intramural Research Program/NIH, Box 12, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
Tomoko
T
Kawai
Ashish
A
Lal
Xiaoling
X
Yang
Stefanie
S
Galban
Krystyna
K
Mazan-Mamczarz
Myriam
M
Gorospe
D020413:3' Untranslated Regions; D000954:Antigens, Surface / Q000378:metabolism*; D015152:Blotting, Northern; D015153:Blotting, Western; D045304:Cytochromes c / Q000032:analysis / Q000096:biosynthesis*; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D004591:Electrophoresis, Polyacrylamide Gel; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020413:3' Untranslated Regions; D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C076751:TIAL1 protein, human; D045304:Cytochromes c