title: Retinoblastoma protein complexes with C/EBP proteins and activates C/EBP-mediated transcription.
abstract: The retinoblastoma protein (RB) recruits histone deacetylase (HDAC) to repress E2F-mediated transactivation that plays a critical role in cell cycle regulation. RB is also involved in activation of expression of a number of tissue specific- and differentiation-related genes. In this study, we examined the mechanism by which RB stimulated the expression of a differentiation-related gene, the surfactant protein D (SP-D), which plays important roles in innate host defense and the regulation of surfactant homeostasis. We demonstrated that RB specifically stimulated the activity of human SP-D gene promoter. The RB family member, p107 but not p130, also increased SP-D promoter activity. Activation by RB was mediated through a NF-IL6 (C/EBP beta) binding motif in the human SP-D promoter, and this sequence specifically bound to C/EBP alpha, C/EBP beta, and C/EBP delta. RB formed stable complexes with all three C/EBP family members. RB small pocket (amino acid residues 379-792), but not the C-pocket (amino acid residues 792-928), was necessary and sufficient for its interaction with C/EBP proteins. Furthermore, we demonstrated that the complexes containing RB and C/EBP proteins directly interacted with C-EBP binding site on DNA. These findings indicate that RB plays a positive, selective, and direct role in the C/EBP-dependent transcriptional regulation of human SP-D expression.
authors.affiliation: The Pulmonary Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: A
authors.initials: A
authors.lastname: Charles
authors.forename: X
authors.initials: X
authors.lastname: Tang
authors.forename: E
authors.initials: E
authors.lastname: Crouch
authors.forename: J S
authors.initials: JS
authors.lastname: Brody
authors.forename: Z X
authors.initials: ZX
authors.lastname: Xiao
mesh_terms: D020816:Amino Acid Motifs; D000596:Amino Acids / Q000737:chemistry; D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D017930:Genes, Reporter; D006367:HeLa Cells; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011506:Proteins; D016160:Retinoblastoma Protein / Q000235:genetics* / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D000596:Amino Acids; D022762:CCAAT-Enhancer-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011506:Proteins; C493844:RBL1 protein, human; C493837:RBL2 protein, human; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D004247:DNA; D006655:Histone Deacetylases