Interaction of anti-proliferative protein Tob with poly(A)-binding protein and inducible poly(A)-binding protein: implication of Tob in translational control.
Tob is a member of an emerging family of anti-proliferative proteins that suppress cell growth when over-expressed. tob mRNA is highly expressed in anergic T cells and over-expression of Tob suppresses transcription of interleukin-2 (IL-2) through its interaction with Smads. Here, we identified two types of cDNA clones coding for poly(A)-binding protein (PABP) and inducible PABP (iPABP) by screening an expression cDNA library with the GST-Tob probe. Co-immunoprecipitation and GST-pull down experiments showed that Tob associated with the carboxyl-terminal region of iPABP. We then found that iPABP, like PABP, was involved in regulation of translation: iPABP enhanced translation of IL-2 mRNA in vitro. The enhanced translation of IL-2 mRNA required the 3'UTR and poly(A) sequences. Tob abrogated the enhancement of translation through its interaction with carboxyl-terminal region of iPABP in vitro. Consistently, over-expression of Tob in NIH3T3 cells, in which exogenous iPABP was stably expressed, resulted in suppression of IL-2 production from the simultaneously transfected IL-2 expression plasmid. Finally, Tob, whose expression was induced by anergic stimulation, was co-immunoprecipitated with iPABP in human T cells. These findings suggest that Tob is involved in the translational suppression of IL-2 mRNA in anergic T cells through its interaction with iPABP.
Okochi
Kentaro
K
Division of Oncology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Suzuki
Toru
T
Inoue
Jun-ichiro
J
Matsuda
Satoru
S
Yamamoto
Tadashi
T
D020413:3' Untranslated Regions; D000818:Animals; D001798:Blood Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D039102:Poly(A)-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D013601:T-Lymphocytes / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
D020413:3' Untranslated Regions; D001798:Blood Proteins; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; C104581:PABPC4 protein, human; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; C098669:TOB1 protein, human; D025521:Tumor Suppressor Proteins