title: p130 mediates TGF-beta-induced cell-cycle arrest in Rb mutant HT-3 cells.
abstract: OBJECTIVE
  The retinoblastoma proteins include Rb and the functionally and structurally related proteins p107 and p130. It has been reported that HT-3 cells are sensitive to TGF-beta growth inhibition, despite the Rb mutation. The purpose of this study was to elucidate the growth-inhibitory mechanism of TGF-beta in Rb mutant HT-3 cells.
  
  
  METHODS
  Growth inhibition by TGF-beta in cervical carcinoma cell lines was evaluated by counting cell numbers. Cell-cycle distribution was determined by staining DNA with propidium iodide (PI) and measured using a flow cytometer. The level of each protein expression was determined by Western blot analysis. To evaluate the assembly of cdk2/p21, cdk2/cyclin E, and E2F-4/p130 complexes by TGF-beta, immunoprecipitation was performed.
  
  
  RESULTS
  TGF-beta inhibited the proliferation of HT-3 cells expressing mutant Rb protein and efficiently induced cell-cycle arrest at G(1) phase. p21 protein level was elevated in TGF-beta-treated HT-3 cells, while other G(1) regulatory protein levels were unaltered. TGF-beta markedly enhanced the binding of p21 with cdk2 but decreased that of cdk2 with cyclin E and inhibited the phosphorylation of p130 but did not change Rb and p107 protein status. We also found that E2F-1 protein level was lower in TGF-beta-treated cells and suggest that this might be the result of enhanced binding between E2F-4 and p130.
  
  
  CONCLUSIONS
  Our results demonstrate that p130, instead of Rb, can mediate growth inhibition by TGF-beta in Rb mutant HT-3 cells.
authors.affiliation: Cancer Research Center, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Hyun Ho
authors.initials: HH
authors.lastname: Choi
authors.forename: Hyun Soon
authors.initials: HS
authors.lastname: Jong
authors.forename: Sang
authors.initials: S
authors.lastname: Hyun Song
authors.forename: Tae
authors.initials: T
authors.lastname: You Kim
authors.forename: Noe
authors.initials: N
authors.lastname: Kyeong Kim
authors.forename: Yung Jue
authors.initials: YJ
authors.lastname: Bang
mesh_terms: D001798:Blood Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D016161:Genes, Retinoblastoma / Q000235:genetics*; D006131:Growth Inhibitors / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D006131:Growth Inhibitors; D011506:Proteins; C493837:RBL2 protein, human; D050717:Retinoblastoma-Like Protein p130; D016212:Transforming Growth Factor beta