title: Post-transcriptional modulation of protein phosphatase PPP2CA and tumor suppressor PTEN by endogenous siRNA cleaved from hairpin within PTEN mRNA 3'UTR in human liver cells.
abstract: OBJECTIVE
  Increasing evidence shows that mRNAs exert regulatory function along with coding proteins. Recently we report that a hairpin within YAP mRNA 3'UTR can modulate the Hippo signaling pathway. PTEN is a tumor suppressor, and is mutated in human cancers. In this study we examined whether PTEN mRNA 3'UTR contained a hairpin structure that could regulate gene regulation at the post-transcriptional level.
  
  
  METHODS
  The secondary structure of PTEN mRNA 3'UTR was analyzed using RNAdraw and RNAstructure. Function of hairpin structure derived from the PTEN mRNA 3'UTR was examined using luciferase reporter assay, RT-PCR and Western blotting. RNA-immunoprecipitation (RIP) assay was used to analyze the interaction between PTEN mRNA and microprocessor Drosha and DGCR8. Endogenous siRNA (esiRNA) derived from PTEN mRNA 3'UTR was identified by RT-PCR and rt-PCR, and its target genes were predicted using RNAhybrid.
  
  
  RESULTS
  A bioinformatics analysis revealed that PTEN mRNA contained a hairpin structure (termed PTEN-sh) within 3'UTR, which markedly increased the reporter activities of AP-1 and NF-κB in 293T cells. Moreover, treatment with PTEN-sh (1 and 2 μg) dose-dependently inhibited the expression of PTEN in human liver L-O2 cells. RIP assay demonstrated that the microprocessor Drosha and DGCR8 was bound to PTEN-sh in L-O2 cells, leading to the cleavage of PTEN-sh from PTEN mRNA 3'UTR. In addition, microprocessor Dicer was involved in the processing of PTEN-sh. Interestingly, esiRNA (termed PTEN-sh-3p21) cleaved from PTEN-sh was identified in 293T cells and human liver tissues, which was found to target the mRNA 3'UTRs of protein phosphatase PPP2CA and PTEN in L-O2 cells. Treatment of L-O2 or Chang liver cells with PTEN-sh-3p21 (50, 100 nmol/L) promoted the cell proliferation in dose- and time-dependent manners.
  
  
  CONCLUSIONS
  The endogenous siRNA (PTEN-sh-3p21) cleaved from PTEN-sh within PTEN mRNA 3'UTR modulates PPP2CA and PTEN at the post-transcriptional level in liver cells.
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Yu-En
authors.initials: YE
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Fu-Quan
authors.initials: FQ
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Jin-Yan
authors.initials: JY
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Guo-Xing
authors.initials: GX
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Biochemistry, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Li-Hong
authors.initials: LH
authors.lastname: Ye
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Department of Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Zhang
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D053487:DEAD-box RNA Helicases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000235:genetics* / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; C474043:DGCR8 protein, human; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C408087:DICER1 protein, human; C517918:DROSHA protein, human; D043244:Ribonuclease III; C517189:PPP2CA protein, human; D054648:Protein Phosphatase 2; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D053487:DEAD-box RNA Helicases