Tristetraprolin down-regulates IL-2 gene expression through AU-rich element-mediated mRNA decay.
Posttranscriptional regulation of IL-2 gene expression at the level of mRNA decay is mediated by an AU-rich element (ARE) found in the 3'-untranslated region. We hypothesized that the ARE-binding protein tristetraprolin (TTP) regulates T lymphocyte IL-2 mRNA decay by interacting with the IL-2 ARE and targeting the transcript for decay. rTTP protein expressed in HeLa cells bound specifically to the IL-2 ARE with high affinity in a gel shift assay. In primary human T lymphocytes, TTP mRNA and protein expression were induced by TCR and CD28 coreceptor stimulation. Using a gel shift assay, we identified a cytoplasmic RNA-binding activity that was induced by TCR and CD28 coreceptor stimulation and bound specifically to the IL-2 ARE sequence. Using anti-TTP Abs, we showed by supershift that this inducible activity contained TTP. We also showed that insertion of the IL-2 ARE sequence into the 3'-untranslated region of a beta-globin reporter construct conferred TTP-dependent mRNA destabilization on the beta-globin reporter. To determine whether TTP also regulates IL-2 gene expression in vivo, we examined IL-2 expression in primary cells from wild-type and TTP knockout mice. Compared with their wild-type counterparts, TCR- and CD28-activated splenocytes and T cells from TTP knockout mice overexpressed IL-2 mRNA and protein. Also, IL-2 mRNA was more stable in activated splenocytes from TTP knockout mice compared with wild-type mice. Taken together, these data suggest that TTP functions to down-regulate IL-2 gene expression through ARE-mediated mRNA decay.
Ogilvie
Rachel L
RL
Microbiology, Immunology and Cancer Biology Graduate Program, University of Minnesota, Minneapolis 55455, USA.
Abelson
Michelle
M
Hau
Heidi H
HH
Vlasova
Irina
I
Blackshear
Perry J
PJ
Bohjanen
Paul R
PR
D000818:Animals; D002457:Cell Extracts / Q000276:immunology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007376:Interleukin-2 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011485:Protein Binding; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D013601:T-Lymphocytes / Q000276:immunology; D014158:Transcription, Genetic; D014162:Transfection; D051816:Tristetraprolin
D002457:Cell Extracts; D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D007376:Interleukin-2; D012333:RNA, Messenger; D051816:Tristetraprolin; C497552:ZFP36 protein, human; C497553:Zfp36 protein, mouse