title: Expression of the HsOrc1 gene, a human ORC1 homolog, is regulated by cell proliferation via the E2F transcription factor.
abstract: The initiation of DNA replication in Saccharomyces cerevisiae requires the action of a multisubunit complex of six proteins known as the origin recognition complex (ORC). The identification of higher eukaryotic homologs of several ORC components suggests a universal role for this complex in DNA replication. We now demonstrate that the expression of one of these homologs is regulated by cell proliferation. Expression of the human Orc1 gene (HsOrc1) is low in quiescent cells, and it is then dramatically induced upon stimulation of cell growth. In contrast, expression of the HsOrc2 gene does not appear to be similarly regulated. We have isolated the promoter that regulates HsOrc1 transcription, and we show that the promoter confers cell growth-dependent expression. We also demonstrate that the cell growth control is largely the consequence of E2F-dependent negative transcription control in quiescent cells. Activation of HsOrc1 transcription following growth stimulation requires G1 cyclin-dependent kinase activity, and forced E2F1 expression can bypass this requirement. These results thus provide a direct link between the initiation of DNA replication and the cell growth regulatory pathway involving G1 cyclin-dependent kinases, the Rb tumor suppressor, and E2F.
authors.affiliation: Department of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ohtani
authors.forename: J
authors.initials: J
authors.lastname: DeGregori
authors.forename: G
authors.initials: G
authors.lastname: Leone
authors.forename: D R
authors.initials: DR
authors.lastname: Herendeen
authors.forename: T J
authors.initials: TJ
authors.lastname: Kelly
authors.forename: J R
authors.initials: JR
authors.lastname: Nevins
mesh_terms: D001483:Base Sequence; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division; D004261:DNA Replication / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005786:Gene Expression Regulation; D018014:Gene Transfer Techniques; D005800:Genes, Fungal; D006801:Humans; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex; D056465:Retinoblastoma-Binding Protein 1; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C497223:ORC1 protein, human; D051738:Origin Recognition Complex; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors