title: Selective repression of growth-regulating cdk2, cyclin E and E2F1 genes in human cell senescence.
abstract: Normal human diploid TIG-1 fibroblasts underwent replicative senescence around 64-68 population doubling levels (PDL) by the irreversible serum-unresponsive G1-growth arrest. Repression of growth-promoting genes was searched in this study. The RT-PCR and Western blot analyses have shown that in senescent TIG-1 cells at PDL64-67, cdk2 and cyclin E were selectively repressed at the mRNA and protein levels even after serum stimulation, and cdc2 and cyclin A were less repressed than cdk2 and cyclin E. Such a specific lack of cdk2 and cyclin E proteins correlated with unphosphorylation of the retinoblastoma gene product (pRB) in senescent cells. Transcription factor E2F1 was also completely repressed at the mRNA and protein levels in senescent TIG-1 cells. Middle-passage cells exhibited active expressions of all the above genes and pRB phosphorylation. Therefore, the present results have indicated the selective repressions of cdk2, cyclin E and E2F1 in senescent cells.
authors.affiliation: Department of Orthopedic Surgery, Kobe University School of Medicine.
authors.forename: S
authors.initials: S
authors.lastname: Kanazawa
authors.forename: Y
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: K
authors.initials: K
authors.lastname: Mizuno
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases; D002352:Carrier Proteins; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins; D002460:Cell Line; D016922:Cellular Senescence / Q000235:genetics*; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000235:genetics* / Q000378:metabolism; D016213:Cyclins / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004622:Embryo, Mammalian; D015870:Gene Expression; D006801:Humans; D008168:Lung; D008969:Molecular Sequence Data; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012194:RNA-Directed DNA Polymerase; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D012333:RNA, Messenger; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D012194:RNA-Directed DNA Polymerase