title: Brn-3b enhances the pro-apoptotic effects of p53 but not its induction of cell cycle arrest by cooperating in trans-activation of bax expression.
abstract: The Brn-3a and Brn-3b transcription factor have opposite and antagonistic effects in neuroblastoma cells since Brn-3a is associated with differentiation whilst Brn-3b enhances proliferation in these cells. In this study, we demonstrate that like Brn-3a, Brn-3b physically interacts with p53. However, whereas Brn-3a repressed p53 mediated Bax expression but cooperated with p53 to increase p21cip1/waf1, this study demonstrated that co-expression of Brn-3b with p53 increases trans-activation of Bax promoter but not p21cip1/waf1. Consequently co-expression of Brn-3b with p53 resulted in enhanced apoptosis, which is in contrast to the increased survival and differentiation, when Brn-3a is co-expressed with p53. For Brn-3b to cooperate with p53 on the Bax promoter, it requires binding sites that flank p53 sites on this promoter. Furthermore, neurons from Brn-3b knock-out (KO) mice were resistant to apoptosis and this correlated with reduced Bax expression upon induction of p53 in neurons lacking Brn-3b compared with controls. Thus, the ability of Brn-3b to interact with p53 and modulate Bax expression may demonstrate an important mechanism that helps to determine the fate of cells when p53 is induced.
authors.affiliation: Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK. v.mahadeo@ich.ucl.ac.uk
authors.forename: Vishwanie S
authors.initials: VS
authors.lastname: Budhram-Mahadeo
authors.forename: Samantha
authors.initials: S
authors.lastname: Bowen
authors.forename: Sonia
authors.initials: S
authors.lastname: Lee
authors.forename: Christina
authors.initials: C
authors.lastname: Perez-Sanchez
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ensor
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Morris
authors.forename: David S
authors.initials: DS
authors.lastname: Latchman
mesh_terms: D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D002453:Cell Cycle; D002460:Cell Line; D002478:Cells, Cultured; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D050820:Transcription Factor Brn-3B / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D018398:Homeodomain Proteins; C085559:Pou4f2 protein, mouse; D050820:Transcription Factor Brn-3B; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein