title: Phosphorylated retinoblastoma protein complexes with pp32 and inhibits pp32-mediated apoptosis.
abstract: The retinoblastoma gene product (Rb) is a tumor suppressor that affects apoptosis paradoxically. Most sporadic cancers inactivate Rb by preferentially targeting the pathway that regulates Rb phosphorylation, resulting in resistance to apoptosis; this contrasts with Rb inactivation by mutation, which is associated with high rates of apoptosis. How phosphorylated Rb protects cells from apoptosis is not well understood, but there is evidence that Rb may sequester a pro-apoptotic nuclear factor. pp32 (ANP32A) is a pro-apoptotic nuclear phosphoprotein, the expression of which is commonly increased in cancer. We report that hyperphosphorylated Rb interacts with pp32 but not with the closely related proteins pp32r1 and pp32r2. We further demonstrate that pp32-Rb interaction inhibits the apoptotic activity of pp32 and stimulates proliferation. These results suggest a mechanism whereby cancer cells gain both a proliferative and survival advantage when Rb is inactivated by hyperphosphorylation.
authors.affiliation: Division of Molecular Pathology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Onikepe
authors.initials: O
authors.lastname: Adegbola
authors.forename: Gary R
authors.initials: GR
authors.lastname: Pasternack
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D050684:E2F Transcription Factors; D005786:Gene Expression Regulation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: C087425:ANP32A protein, human; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D011506:Proteins; D016601:RNA-Binding Proteins; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D013912:Threonine