title: Tristetraprolin inhibits poly(A)-tail synthesis in nuclear mRNA that contains AU-rich elements by interacting with poly(A)-binding protein nuclear 1.
abstract: BACKGROUND
  Tristetraprolin binds mRNA AU-rich elements and thereby facilitates the destabilization of mature mRNA in the cytosol.
  
  
  RESULTS
  To understand how tristetraprolin mechanistically functions, we biopanned with a phage-display library for proteins that interact with tristetraprolin and retrieved, among others, a fragment of poly(A)-binding protein nuclear 1, which assists in the 3'-polyadenylation of mRNA by binding to immature poly(A) tails and thereby increases the activity of poly(A) polymerase, which is directly responsible for polyadenylation. The tristetraprolin/poly(A)-binding protein nuclear 1 interaction was characterized using tristetraprolin and poly(A)-binding protein nuclear 1 deletion mutants in pull-down and co-immunoprecipitation assays. Tristetraprolin interacted with the carboxyl-terminal region of poly(A)-binding protein nuclear 1 via its tandem zinc finger domain and another region. Although tristetraprolin and poly(A)-binding protein nuclear 1 are located in both the cytoplasm and the nucleus, they interacted in vivo in only the nucleus. In vitro, tristetraprolin bound both poly(A)-binding protein nuclear 1 and poly(A) polymerase and thereby inhibited polyadenylation of AU-rich element-containing mRNAs encoding tumor necrosis factor α, GM-CSF, and interleukin-10. A tandem zinc finger domain-deleted tristetraprolin mutant was a less effective inhibitor. Expression of a tristetraprolin mutant restricted to the nucleus resulted in downregulation of an AU-rich element-containing tumor necrosis factor α/luciferase mRNA construct.
  
  
  CONCLUSIONS
  In addition to its known cytosolic mRNA-degrading function, tristetraprolin inhibits poly(A) tail synthesis by interacting with poly(A)-binding protein nuclear 1 in the nucleus to regulate expression of AU-rich element-containing mRNA.
authors: Graduate Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan.
authors: Yu-Lun
authors: YL
authors: Su
authors: Shun-Chang
authors: SC
authors: Wang
authors: Pei-Yu
authors: PY
authors: Chiang
authors: Nien-Yi
authors: NY
authors: Lin
authors: Yu-Fang
authors: YF
authors: Shen
authors: Geen-Dong
authors: GD
authors: Chang
authors: Ching-Jin
authors: CJ
authors: Chang
mesh_terms: D063307:AU Rich Elements; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008156:Luciferases / Q000235:genetics; D051379:Mice; D011061:Poly A / Q000096:biosynthesis*; D039103:Poly(A)-Binding Protein II / Q000737:chemistry / Q000378:metabolism*; D026723:Polyadenylation; D011062:Polynucleotide Adenylyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D051816:Tristetraprolin / Q000737:chemistry / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: D039103:Poly(A)-Binding Protein II; D012333:RNA, Messenger; D051816:Tristetraprolin; D014409:Tumor Necrosis Factor-alpha; D011061:Poly A; D008156:Luciferases; D011062:Polynucleotide Adenylyltransferase