Reduced nuclear export of HuR mRNA by HuR is linked to the loss of HuR in replicative senescence.
The RNA-binding protein, HuR, associates with the HuR mRNA, but the consequences of this interaction are unknown. Here, we use human diploid fibroblasts (HDFs) and cervical carcinoma cells to study this regulatory paradigm. Ectopic overexpression of HuR potently enhanced the translation and cytoplasmic levels of endogenous HuR, but did not affect HuR mRNA levels. Inhibition of CRM1 function by Lemptomycin B or by knockdown of CRM1 greatly diminished the cytoplasmic levels of endogenous HuR mRNA and hence blocked the induction of endogenous HuR by exogenous HuR. Further studies showed that HuR interacted with the 3'-untranslated region (UTR) of HuR and that overexpression of HuR increased the cytoplasmic levels of a chimeric luciferase-HuR 3'-UTR reporter transcript, as well as luciferase activity; conversely, HuR knockdown reduced both parameters. Moreover, the loss of HuR in senescent, late-passage HDFs was accompanied by a reduced cytoplasmic presence of endogenous HuR mRNA, ectopic Luc-HuR-3'UTR reporter transcript, and luciferase activity relative to what was observed in young, early-passage cells. Our results reveal a positive feedback mechanism for the regulation of HuR, which may play an important role in the regulation of HuR during replicative senescence.
Yi
Jie
J
Research Center on Aging, Department of Biochemistry and Molecular Biology, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100083, USA.
Chang
Na
N
Liu
Xinwen
X
Guo
Gaier
G
Xue
Lixiang
L
Tong
Tanjun
T
Gorospe
Myriam
M
Wang
Wengong
W
D020413:3' Untranslated Regions; D021581:Active Transport, Cell Nucleus; D000954:Antigens, Surface / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D016922:Cellular Senescence; D003593:Cytoplasm / Q000378:metabolism; D004261:DNA Replication; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism
D020413:3' Untranslated Regions; D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins