title: A systematic search for downstream mediators of tumor suppressor function of p53 reveals a major role of BTG2 in suppression of Ras-induced transformation.
abstract: Factors that mediate p53 tumor suppressor activity remain largely unknown. In this study we describe a systematic approach to identify downstream mediators of tumor suppressor function of p53, consisting of global gene expression profiling, focused short hairpin RNA (shRNA) library creation, and functional selection of genetic elements cooperating with oncogenic Ras in cell transformation. This approach is based on our finding that repression of gene expression is a major event, occurring in response to p53 inactivation during transformation and immortalization of primary cells. Functional analysis of the subset of genes universally down-regulated in the cells that lacked functional p53 revealed BTG2 as a major downstream effector of p53-dependent proliferation arrest of mouse and human fibroblasts transduced with oncogenic Ras. shRNA-mediated knockdown of BTG2 cooperates with oncogenic Ras to transform primary mouse fibroblasts containing wild-type transcriptionally active p53. Repression of BTG2 results in up-regulation of cyclins D1 and E1 and phosphorylation of Rb and, in cooperation with other oncogenic elements, induces neoplastic transformation of primary human fibroblasts. BTG2 expression was found to be significantly reduced in a large proportion of human kidney and breast carcinomas, suggesting that BTG2 is a tumor suppressor that links p53 and Rb pathways in human tumorigenesis.
authors.affiliation: Department of Molecular Genetics, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Boiko
authors.forename: Sarah
authors.initials: S
authors.lastname: Porteous
authors.forename: Olga V
authors.initials: OV
authors.lastname: Razorenova
authors.forename: Vadim I
authors.initials: VI
authors.lastname: Krivokrysenko
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Williams
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Gudkov
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D019927:Cyclin E; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D015723:Gene Library; D016161:Genes, Retinoblastoma / Q000187:drug effects / Q000502:physiology; D016147:Genes, Tumor Suppressor / Q000187:drug effects; D011905:Genes, ras / Q000235:genetics / Q000502:physiology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D009369:Neoplasms / Q000235:genetics; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D040081:Protein Array Analysis / Q000379:methods; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
chemical_list: C475820:CCNE1 protein, human; D019927:Cyclin E; D017874:Immediate-Early Proteins; D015513:Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; C070114:BTG2 protein, human