Differential expression and functional analysis of the tristetraprolin family during early differentiation of 3T3-L1 preadipocytes.
The tristetraprolin (TTP) family comprises zinc finger-containing AU-rich element (ARE)-binding proteins consisting of three major members: TTP, ZFP36L1, and ZFP36L2. The present study generated specific antibodies against each TTP member to evaluate its expression during differentiation of 3T3-L1 preadipocytes. In contrast to the inducible expression of TTP, results indicated constitutive expression of ZFP36L1 and ZFP36L2 in 3T3-L1 preadipocytes and their phosphorylation in response to differentiation signals. Physical RNA pull-down and functional luciferase assays revealed that ZFP36L1 and ZFP36L2 bound to the 3' untranslated region (UTR) of MAPK phosphatase-1 (MKP-1) mRNA and downregulated Mkp-1 3'UTR-mediated luciferase activity. Mkp-1 is an immediate early gene for which the mRNA is transiently expressed in response to differentiation signals. The half-life of Mkp-1 mRNA was longer at 30 min of induction than at 1 h and 2 h of induction. Knockdown of TTP or ZFP36L2 increased the Mkp-1 mRNA half-life at 1 h of induction. Knockdown of ZFP36L1, but not ZFP36L2, increased Mkp-1 mRNA basal levels via mRNA stabilization and downregulated ERK activation. Differentiation induced phosphorylation of ZFP36L1 through ERK and AKT signals. Phosphorylated ZFP36L1 then interacted with 14-3-3, which might decrease its mRNA destabilizing activity. Inhibition of adipogenesis also occurred in ZFP36L1 and TTP knockdown cells. The findings indicate that the differential expression of TTP family members regulates immediate early gene expression and modulates adipogenesis.
Institute of Biological Chemistry, Academia Sinica, 128, Academia Road Sec 2, Nankang, Taipei 115, Taiwan.
Nien-Yi
NY
Lin
Tzi-Yang
TY
Lin
Wen-Hsuan
WH
Yang
Shun-Chang
SC
Wang
Kuan-Ting
KT
Wang
Yu-Lun
YL
Su
Yu-Wun
YW
Jiang
Geen-Dong
GD
Chang
Ching-Jin
CJ
Chang
D048948:14-3-3 Proteins / Q000378:metabolism; D041721:3T3-L1 Cells; D000818:Animals; D051817:Butyrate Response Factor 1; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051816:Tristetraprolin / Q000235:genetics / Q000378:metabolism*
D048948:14-3-3 Proteins; D051817:Butyrate Response Factor 1; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D051816:Tristetraprolin; C497553:Zfp36 protein, mouse; C488431:Zfp36l1 protein, mouse; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse